The DESC Engineer Redefines Work

John Baltz Improved hydrocarbon recovery is the focus of the Production Steve Bumgardner Enhancement Group (PEG), which combines expertise from Schlumberger Jeff Hatlen Henry Swartzlander Wireline & Testing, Dowell and Anadrill to develop a coordinated field Texaco Exploration and Production Inc. Bakersfield, California, USA management plan. Their success depends on building new kinds of working relationships between oil and service companies. Here is a look Phil Basham Al Blessen at one of the most intimate of those relationships, the DESC Design and Fred Sarrafian Mark Schneider Evaluation Services for Clients program. In this service, a Dowell engineer Texaco Exploration and Production Inc. works in the client office and with oil company engineers to analyze wells Denver, Colorado, USA that are candidates for production improvement and to develop treatments Dennis Clayton Tim Frank to enhance well productivity. Doug Gordon Bill Taylor Mitch Kniffin arrives On a typical day like this, follow Mitch Shell Western E&P Inc. at the Texaco office Kniffin around and you might conclude he’s Houston, Texas, USA in Denver at 7:00 a hard-working Texaco engineer. There is lit- in the morning, tle obvious evidence that he’s a Dowell Mitch Kniffin wearing a Texaco engineer, one of 95 assigned to client offices Denver, Colorado windbreaker with in North America. By the end of 1995, an “Star-Quality estimated 175 engineers worldwide will be Fred Mueller Ambassador” assigned to customer offices in the DESC Bakersfield, California embossed on the program, short for Design and Evaluation front. The jacket is a point of pride: he’s part Services for Clients. Duncan Newlands of a team recognized for saving the company For both Dowell and operating companies D.J. White $38 million in drilling costs in the last two like Texaco, the DESC program provides sig- Houston, Texas years. nificant benefits. DESC engineers are dedi- Kniffin sheds the jacket, grabs a notepad cated to serving a single customer, cutting For help in preparation of this article, thanks to Larry and heads to the morning meeting. He joins cost, improving quality and raising produc- Behrmann, Schlumberger Wireline & Testing, Rosharon, a half-dozen drilling engineers seated tivity. They contribute years of experience in Texas, USA; Pierre Celle and Claude Vercaemer, Dowell, Montrouge, France; Curtis Boney, Larry Brumit, Doug around a teleconference phone discussing completion engineering, and when they Pferdehirt and Bobby Poe, Dowell, Sugar Land, Texas; the previous day’s well reports with Texaco’s move into an oil company office, they are Anil Mathur, Jerry Richards and Grafton Withers, Dowell, operations groups in Midland, Texas, USA practically self-sufficient, bringing their own Houston, Texas; Bobbie Joines, Dowell, Denver, Colorado; Jay Haskell, Wireline & Testing, Houston; Joe Mach, and other locations. The teams discuss good networked workstation, a bookshelf of Wireline & Testing, Sugar Land, Texas; Ken Nolte, Dowell, news and bad, and debate solutions. When Dowell software and a modem. The oil Tulsa, Oklahoma, USA; Maripat Sexton, Texaco, Houston. the agenda turns to hydraulic fracturing in company provides an office with a desk and In this article, DART, DESC (Design and Evaluation Services for Clients), FracIPR, NODAL and STIMPAC are marks of West Texas, all eyes land on Kniffin. chair, phone and electricity, and access to Schlumberger; Unigraf is a mark of Control Data Corpora- well files and company experts. tion; VAX and VMS are marks of Digital Equipment The oil company gets a seasoned engineer Corporation. with a fresh perspective. Dowell gets a

40 Oilfield Review Cementing Costs richer understanding of client needs and 60 ■Reduction in total process cost is cen- improved access to opportunities for well Benchmark costs 50 tral to the DESC pro- treatment services. Both parties benefit from Alliance costs gram. In east Texas, daily contact that builds trust, which stimu- DESC engineers lates the cross-pollination of ideas. This can- 40 working in an did exchange results in easier acceptance of alliance with the operating company new ideas and faster development of solu- 30 helped reduce the tions. As management consultants say, it’s a cost of cementing win-win scenario (right). 20 and fracturing. This

Five years have passed since Bob Fagan Thousands of dollars was accomplished became the first Dowell engineer posted in mainly through use 10 Benchmark average – $28,580 of software tools for a client office, at Chevron in Bakersfield, Alliance average – $20,622 stimulation optimiza- California. In the short time since its incep- 0 tion, reduction in tion, the DESC program has grown quickly May July Sept Nov Jan Mar May July Sept Nov Jan standby equipment and evolved to meet changing market and optimization of demands (next page). Here is a look at how fluids engineering. Fracturing Costs the DESC program works, and a tour of case 500 studies—in Texaco and in Shell—to see how DESC engineers operate day to day. Benchmark costs 400 Alliance costs Breaking Workplace Barriers Given the sometimes adversarial relation- 300 ships that formerly existed between service and operating companies, placing a contractor in an oil company office may seem like 200 an unusual move. Yet, the idea is not new. In Thousands of dollars Schlumberger, three notable incarnations of 100 this strategy foreshadowed the DESC pro- Benchmark average – $245,148 gram. In the 1960s, Schlumberger engineers Alliance average – $195,605 0 were placed in customer offices to operate May July Sept Nov Jan Mar May July Sept Nov Jan the complex DART radio log transmission network, which conveyed data to the main- land from rigs in the Gulf of Mexico.1 In the changed, but not usually how you worked. In the early 1990s, the DESC program early 1980s, log interpreters were installed in The contractor mainly operated a system for redrew the boundaries of that relationship. client offices, operating the VAX-based the client and fulfilled client requests on a Rather than work on a contractual basis, Client Log Interpretation Center (CLIC). This per-bid basis. Placement of the engineer the DESC engineer would look for wells evolved into the third incarnation, the PC- and equipment in the oil company office that could be more productive, and and workstation-based Dedicated Client was for expediency and took place within Center of today. the constraints of a conventional contrac- In the DART and CLIC programs, the rela- tual relationship. There were happy coinci- 1. Eaton FM and Decker GJ: “Digital Transmission of Well Logs by Radio and Telephone,” Journal of tionship between contractor and operator dences of the supplier consulting to the oil Petroleum Technology 18 (February 1966): 151-154. did not change. Where you worked company, but that was not part of the plan. The relationship between the two companies was generally maintained at the tradi- tional arm’s length.

Summer 1995 41 Clients start Rig count in North asking for DESC America reaches engineers. VMS PC lowest level in 40 years. DESC engineer candidates begin First Wireline Bob Fagan Formal training 3- to 6-month engineers co- Dowell begins shift becomes first begins for DESC training with the placed with DESC from VMS-based Dowell engineer engineers. Performance engineers for workstation to placed in an Enhancement enhanced service PC platform, with oil company Twenty DESC Group (PEG) in integration. transition of office–Chevron, placements. Houston. CADE programs. Bakersfield, Bernard Fraboulet DESC toolbox California, USA. The term becomes first Industry-wide expanded to include Engaged mostly in DESC Design DESC engineer interest increases program to calculate Expansion in DESC logistical planning and Evaluation outside North in total quality return on investment placements both to boost service Services for America, for Elf in management of remedial driving and driven by efficiency. Clients coined. Pau, France. strategies. treatments. growth in alliances.

1990 1991 1992 1993 1994 1995

Equipped with Qualifications DESC program Oil company- Strong growth of Introduction of four VMS-based defined for refocused on supplier alliances alliances: 16 of new programs to workstation, 2400- Dowell engineers identifying candidate start to become Dowell’s 20 largest accelerate candidate bit-per-second posted in client wells for remedial reality. clients engaged in recognition from ~2 (bps) modem, offices. treatment to increase some type of days per well to 1/2 Schlumberger CADE programs, productivity, alliance. day. gains full control of spreadsheet, word Ten engineers called candidate Dowell, acquiring Dowell PhDs at DESC engineers editor, Unigraf placed in client recognition. the remaining 50% area level provide connect to graphics package. offices, all at Dowell initiative. Systems Analysis of Dowell- high-level technical Schlumberger Module (SAM) Schlumberger, support. network using introduced, ending a 14,400+ bps modem computerized successful 33-year and Internet prediction of well joint venture with protocol. performance. Dow Chemical.

200 2100

150 Worldwide rig count 1900 100 1700 50 DESC engineers orldwide rig count W

# of DESC engineers 0 1500 ■Time line of DESC program evolution.

develop strategies to bring them up to full tional engineer to focus on finding low-cost advantage of a crew that is 20 miles [32 km] potential. This approach, called candidate means of enhancing productivity. Many oil from the well instead of 200 miles [322 recognition, would increase opportunities companies were ready to consider this new km]. Early in the DESC program, it became for Dowell that were independent of the way to do business. clear that simply having a DESC engineer in shrinking rig count, and would enhance For the early DESC engineers, candidate house significantly improved logistics to the productivity for the oil company. recognition was not the sole activity. The benefit of both Dowell and its clients. At this time, the idea of a service com- first opportunities were improving the logis- Until about 1992, logistics remained a pany representative posted in the office was tics of well treatment. This involved collabo- key activity for the handful of DESC engi- anathema to many oil companies. Yet, with rating with the drilling or production depart- neers. By the end of 1992, the focus shifted the advent of total quality management ment to better coordinate Dowell crews, to emphasize candidate recognition, which (TQM), the DESC program offered an addi- equipment and delivery of raw materials. today remains the core of the program Small improvements in logistics yielded (next page, middle). This umbrella covers large gains in productivity. For example, bet- the range of pumping and fluids engineer- ter scheduling can allow a crew to perform two jobs per day instead of one, or can take

42 Oilfield Review ing services, including fracturing, sand con- being regarded as a guest to being accepted ulation and candidate recognition. This trol, coiled tubing services, acidizing, as one of the team. Foremost, the engineer includes development of proficiency with drilling fluids and cementing. In 1995, as must be able to work within the oil com- NODAL production systems analysis and Schlumberger Wireline & Testing engineers pany culture to develop support for optimal other Dowell software used in candidate are being located in client offices along solutions. recognition. It also includes training in perfo- with Dowell engineers, the umbrella now “When I first arrived at Shell,” Newlands ration, pressure transient and decline curve includes log input to completion services. said, “the most skeptical production engi- analyses, fracture theory and fracture fluids Candidate recognition is expected to grow neer was the first to let me design a frac engineering. in importance in mature markets, as opera- job. When that job went off without a The engineer then is posted to an oil com- tors seek to extend the life of aging fields. hitch, that went a long way to winning the pany, usually in the production or drilling With candidate recognition as the focus, a trust of everyone.” department, and begins gradual assimila- new contractor-operator relationship had To build the range of needed skills, most tion. Three case studies show how DESC been cemented (bottom). “In the old way of new DESC engineers receive three to six engineers work today—two in Texaco, in working,” said Duncan Newlands, a DESC months of training in the Production the context of a single-vendor alliance, and engineer for Shell Western E&P in Houston, Enhancement Group (PEG) in Houston. The one in Shell, in a more conventional rela- “the client might say, ‘Here’s my pump PEG comprises specialists from Wireline & tionship (see “Alliances in the Oil Field,” schedule. Be ready Testing, Dowell and Anadrill, who identify page 26). to roll Tuesday wells with potential for increased produc- morning at 5.’ Now tion and develop an integrated program to DESC in an Alliance: Texaco the client might raise well productivity. Client interest in Texaco has undertaken a significant change say, ‘Work with PEG projects is funneled through Schlum- that involves not only the sale of assets and our team to berger sales engineers throughout North refocusing on core businesses, but a dra- develop a comple- America. PEG engineers then review client matic culture shift. This shift accelerated tion plan for this well files and submit bids for well treatment with the 1994 launch of a worldwide plan well that gives both based on the analysis. for growth, with a top-down emphasis on companies the highest value.’ Oil compa- In the PEG program, Dowell engineers TQM—a focus on continuously examining nies are beginning to realize there’s benefit learn the essentials of well performance sim- how things are done and taking steps to find in trusting us to meet or exceed their criteria better ways, including different ways of for job performance.” working with contractors.2 Given the large scope of responsibilities “Historically, we placed a great deal of the DESC program places on Dowell engi- Potential calculated emphasis on the lowest possible bid,” said neers, training had to rise to the challenge. with SAM and John Baltz, Texaco’s assistant division man- FracIPR software The DESC program starts with engineers Gap ager in Bakersfield. “All that changed when who have mastered the basics. Those picked we stopped focusing on price alone and

for the program typically have had at least oduction rate placed more emphasis on the significant three years of experience in completion and Pr Actual few oil and gas fields, technologies and rela- fluids engineering and have demonstrated tionships that contribute to performance.” both entrepreneurial spirit and interpersonal Five years ago, service companies were Time skills. These skills are essential, since the job requires technical proficiency, business acu- ■Closing the gap. Candidate recognition involves first identifying underproducing 2. For a review of TQM principles and application of men and diplomacy. When first installed in those principles in the oil field: wells and, using software tools like the Sys- the client office, the engineer must win the Burnett N, Harrigan J, Jeffries J, Lebsack T, Mach J, tems Analysis Module (SAM) and FracIPR, Mullen D, Pajot D, Rat F, Robson M, Theys P and confidence of oil company colleagues and, calculating what the well could produce. Wohlwend H: “Quality,” Oilfield Review 5, no. 4 to be most effective, must progress from Second, well treatment strategies are (October 1993): 46-59. developed to “close the gap” between what is and what could be.

DESC Engineer Main Responsibilities

•Work with client on treatment design •Collect and evaluate post-treatment data •Develop general knowledge of and evaluation (performance versus expectations) Schlumberger product lines outside •Collect and evaluate data for candidate •Provide benchmarks for continuous Dowell recognition treatment design improvement •Identify, coordinate and implement addi- •Identify, coordinate and implement •Document results and supply benefits to tional Dowell services and additional treatment or design changes for the client and to Dowell technical sup- Schlumberger product lines based on improved well performance and port and management client needs. economics •Enlist appropriate technical support when necessary •Identify and implement process improvements with client

Summer 1995 43 6 Fred Mueller started as a DESC engineer for Texaco in 1993, working in the Kern River field in an alliance exclusive to Texaco’s 5 Bakersfield division (next page, bottom right). Mueller is engaged in three main projects—resin packs, research on how 4 hydraulic fracture design affects steamdrive efficiency, and optimization of resource 3 utilization (left and below left). The foremost technical ime on location, hr

T 2 challenge, and work that occupies most of his energy, is the 1 resin pack. An overview of Kern River production engineering shows why this is a priority. 0 The Kern River field has some of the tight- Sept Oct Nov Dec Jan Feb March Sept Oct est margins in North America. The oil is 1993 1994 heavy and requires steamflooding for production, which averages less than 20 barrels of ■Resource optimization means less time per treatment job. At the beginning of the oil per day (BOPD) per well. Still, the field is Texaco DESC program in Kern River, Texaco engineers would call for service early advantaged because productive intervals are because time management was not a priority. As a result, the pumping crew might spend at least five hours at each job, sometimes just waiting to get in the hole. Mueller’s typically less than 1500 ft [460 m] deep, and close relationship with Texaco colleagues allowed him to work with them to improve oil saturations are high. Texaco, the largest scheduling and remove bottlenecks and redundancies. “Once Texaco learned how much operator in the field, produces more than time the pumping crews needed,” he said “and that time was a key element in our prof- 80,000 BOPD from 4600 wells. The 96-year- itability, Texaco worked toward just-in-time pumping.” This cut time at the wellsite from five to four hours per job, allowing crews to perform more jobs per day. old field is the fifth largest in the United States, with estimated reserves of 518 million ■A virtual Dowell barrels. research center. The largest operating expense for Texaco Jorge Manrique of is making steam, which runs $80 million a Dowell (left) and year. Extracting the most oil per calorie of Fred Mueller, confer on Manrique’s mod- gas burned to make steam—called the fuel- eling in Kern River to oil ratio—is the most important driver of understand steam- efficiency. flood efficiency—the After personnel costs, the next driver is amount of energy contract work expenses. The bulk of contract required to produce one barrel of oil. work—and here’s where resin packs come Manrique, a PhD in—is removal of sand. Texaco walks a thin engineer with line between sand production and steam Dowell in Denver, injection. Too much steam, and wells sand is working with Mueller and up prematurely. Too little steam, and wells Texaco colleagues don’t produce efficiently. Even at the right in Bakersfield. balance, 2 to 3 tons of sand are produced per day, adding up to an expensive problem. If sand production can be stemmed, then viewed guardedly and kept at a distance. work together to drive down each other’s Texaco can achieve two objectives: cut costs Today, many suppliers have offices in Tex- cost and improve productivity. Both parties related to sanding, and deliver the optimal aco facilities and work shoulder to shoulder share in the risks and rewards. In other steam injection rate to achieve the highest with Texaco colleagues. words, it has to have an alignment of goals possible fuel-oil ratio. Texaco has moved aggressively into that motivates both parties to commit to Curbing sand production with gravel packs numerous alliances with key suppliers. continuously improve how they work.” and slotted liners provided mixed results. In Texaco and Dowell entered into a US Two examples of DESC engineers provid- 1993, Mueller recommended a STIMPAC ser- pumping service alliance on March 1, 1995, ing different kinds of service for Texaco are vice—fracturing combined with gravel pack- for all of Texaco’s cementing and stimula- in the Kern River field, of Bakersfield, Cali- tion needs. fornia, and the Permian Basin of West Texas. “An alliance is more than just a single- In both places, DESC service started within vendor contract with an attractive price,” a local alliance. These have evolved into a said Fred Sarrafian, assistant division man- Texaco-Dowell pumping alliance covering ager for Texaco in Denver. “It means that we all the US. Texaco: Extending the Life of the Kern 44 River Field Oilfield Review ■Rigging up in the land of the eight- minute frac. Produc- ing wells are fractured and packed with resin-coasted sand in the Kern River field. The frac jobs are small, pumping 10,000 to 25,000 lbm [4535 to 11,340 kg] of proppant to produce fracture half-lengths of 50 to 100 ft [15 to 30 m]. Texaco wells follow a “five-spot” pattern: one injector surrounded by four producers.

■The Kern River skirts the southern edge of the Kern River field in Bakersfield, California.

■What phenolic resin coating does to ing. The treatments halted sand production top). Uncoated sand would not work in proppant. This pack of sand is held without restricting the flow of oil. At the Kern River because low closure stress of the together by heat-induced fusing of a phenolic resin. It has a permeability in the same time, Steve Bumgardner, a Texaco shallow wells would not hold the sand in darcy range, and enough mechanical petroleum engineer, introduced the more place. Also, the high viscosity of the crude strength to hold back the flow of sand at economical idea of using resin-coated sand would drive uncoated sand into the well. typical production rates. to control formation sand production. While posted in the Rocky Mountains, A resin pack involves filling a hydraulic Bumgardner had worked with resin packs. fracture with resin-coated sand. The resin, in “Fred and I bounced around ideas for this case a phenol, is activated mainly by designing resin packs for Kern River,” Bum- the 220°F [104°C] downhole temperature. gardner said. Texaco and Dowell worked The fused resin binds the coated sand grains into a solid but high-permeability pack that stops sand production (above, far left and

Summer 1995 45 together to optimize the treatments, looking at sand size, resin type, pump schedule and fracturing fluids. Proof came at the end of 1994. In a 12- U N I T E D S T A T E S well pilot study, 10 wells were improved. Average production per well rose from 16 to 27 BOPD, and monthly cost of well servic- ■Texaco properties, ing dropped from $1549 to $540—a 70% leased and owned, Eastern in the Permian Shelf increase in production and a 65% reduction New Mexico Basin of New Mex- in maintenance cost. The two wells that did n Shelf Midland ico and West Texas. not improve failed uphole, not in the treated Basin The Permian Basin Delaware occupies about the zone. Based on these results, the Bakersfield Northeaster Basin Central Basin Texas same area as the division plans to perform resin packs in 170 Platform Irish Republic. wells this year. D The key to success of the process was the i ab lo collaboration of Bumgardner and Mueller. P l at “My expertise is in fracturing technology,” fo rm Bumgardner said, “but I don’t need to know M E X I C O Southern Shelf Val Verde the exact fluid compositions and equipment Basin characteristics. Combining my expertise Marfa uachita-Marathon O Stru Basin ctu with Fred’s knowledge and experience in ra l B 0 km 120 e fracturing and pumping made for the most lt effective team.” 0 miles 75 “We used to try to be the expert in everything,” said Henry Swartzlander, a Texaco operations manager who oversees about half of Texaco’s Kern River assets. “This ulti- Basin (above). The region has yielded 30 mately hurt our profitability because we billion of the 87 billion barrels of oil pro- groups, having started as a Texaco DESC didn’t have the time, people and compe- duced in the United States in 70 years. Pro- engineer in Midland in 1992, before moving tency to excel at everything. Having people duction today is 38,000 barrels of oil equiv- to Denver in 1994. like Fred here allows us to tap the world- alent (BOE) per day, and although it is Along with fracture design, Kniffin also wide expertise of Dowell, which reduces declining slowly, it is still the most prolific has been coordinating evaluation of meth- our cycle time by shortening our learning area outside of Alaska.3 Proved reserves are ods to find the optimal fracturing program. curve. Ultimately, faster cycle time improves 5.4 billion BOE. For this challenging area, what works in one our profitability.” The Permian Basin is a hodgepodge of well, may fail in another well that appears A key to improving cycle time for Texaco depositional environments, including reefs to have identical properties. is daily give and take with Mueller that and shelf carbonates, turbidites, beach and The main challenge is avoiding near-well- increases knowledge of available technol- nearshore sands and sabkha.4 Well produc- bore screenout: bridging of proppant in the ogy. Another means is Mueller’s lunchtime tivity is 20 to 100 BOPD, with the typical fracture near the wellbore, which halts fluid seminars on a variety of well and fluids well making 35 BOPD. Texaco conducts entry and propagation of the fracture. Well- engineering topics, such as cementing, frac- one of the most active drilling programs in bore screenouts can occur in the complex turing high-permeability reservoirs, sieve the basin, and operates some 15,000 wells. connection between the wellbore and frac- analysis and basics of cement additives. Following the diversity of depositional envi- ture entrance (next page top). This complex- “The ultimate test of the success of this ronments, well depths vary from 3500 to ity, called tortuosity, generally results from program,” said Jeff Hatlen, a Texaco opera- 28,000 ft [1066 to 8534 m]. About half of too large an angle between the perforation tions manager in Kern River, “is improved Texaco’s production is from carbonates, and and the plane of the natural fracture, or from profitablity of both companies. My interests the bulk of work for DESC Engineer Mitch multiple fractures that may or may not coa- are not limited to reducing costs. I’m inter- Kniffin centers on fracturing tight dolomite lesce into a preferred single fracture (next ested in developing opportunities and mak- oil and gas reservoirs. page bottom). Coalescing of fractures is ing more money. If Dowell can help me do Fracturing is big business for Texaco in the likely to produce tortuosity when perfora- that, I’m willing to share that success.” Permian Basin. In 1994, the company fraced tions are not aligned with the principal 200 wells—with up to three fracs per stress in the formation. Multiple fractures Texaco: Fracs in the Permian Basin well—and if the pace of drilling holds, the produce narrower fracture channels and More than one third of the hydrocarbons number may rise to 250 this year. With one more surface area for fluid loss through the produced in the United States since the well fraced every two days, Kniffin monitors fracture faces. Both coalescing and multiple 1920s has come from the 29,000-square- the progress of about 30 wells at one time. fracs increase the likelihood of proppant mile [75,100 km2] area of West Texas and From the Texaco division headquarters in accumulation near the wellbore and a result- southeast New Mexico called the Permian Denver, Kniffin works with engineers in ing screenout. Reducing fracture entrance both Denver and Midland who oversee the Permian Basin operations. He knows both

46 Oilfield Review str str Maximum Maximum ess dir ess dir Path of fracture ection ection Perf

Perf angle >30°

Path of ° ° fractures 0 < angle <30

■Near-wellbore restrictions that contribute to screenout. A goal of perforation and fracturing design is to minimize tortuosity of the connection between the perforation and the fracture, and thereby develop fractures with the highest possible conductivity. Modeling studies show that fractures typically extend from the base of a perforation at the cement-formation interface and travel some distance around the wellbore to reorient into the plane parallel to the maximum horizontal stress. A main concern is the development of multiple fractures, which produce flow restrictions that lead to screenout. Experimental evidence suggests that multiple fractures tend to form when the angle between the perforation and maximum stress direction is greater than 0° but less than 30°.

sure, fluid density and additive composition Rhomboids and concentrations. “As our engineers focus more on well planning, they still collaborate on treatment design,” said Phil Basham, a Texaco drilling team leader. “But I see Mitch taking a larger role in designing and managing jobs. We are more productive if we rely on Dowell for job execution and have our people concentrate on well planning, process improvement, cost reduction opportunities and technology applications.” ■Coalescence of fractures as a cause of tortuosity. How fractures evolve from perforations Adding responsibility and accountability can contribute to pressure drop, and proppant bridging, in the region near the wellbore. to a contractor has “broken down our As fractures propagate, they may form an overlapping arrangement, called en echelon, paradigms,” said Al Blessen, Texaco drilling and eventually connect. Isolated rhomboids of rock develop between the connecting tails of the fractures. Small fractures associated with these rhomboids are suspected to con- engineer. “Now we want to find the best tribute to the pressure drop that leads to early bridging of proppant. Limiting the height practices, rather than those that we have of the fractured interval is thought to reduce the number of rhomboids, and thus the always relied on and are comfortable with.” mechanism that leads to bridging. An example of a paradigm break was in Texaco’s design of Permian Basin comple- effects is required for proppant to flow unim- With up to four jobs per week, Kniffin tions. Texaco’s practice was to complete peded, and for the fracture to reach maxi- can’t attend each one. For critical jobs, he wells using three strings of casing: surface, mum length and conductivity (see “Getting relies on a double cellular phone connec- intermediate and production string. This the Most from Perfs,” next page). tion between his office in Denver and the approach was perceived to minimize risk of Kniffin works with Texaco engineers to Dowell crew at the wellsite in West Texas. loss of well control from lost circulation or determine optimum fracture dimensions and One line provides a voice connection. The water entry (right). develop a treatment pumping schedule, other furnishes real-time, on-screen moni- contributing to Texaco’s saving at least one toring of up to 10 variables during the job, 3. Permian Basin Petroleum Association, Midland, Texas, engineering day per frac design. He tracks typically including pump rate, surface pres- USA, personal communication, May 1995. the performance of treatments to discern 4. Sabkha encompasses depositional environments just above the high-tide line in an arid setting. It includes patterns that lead to success or failure. This evaporites, tidal flood and eolian deposits. is a critical step, since process improvement is integral to the success of the alliance.

Summer 1995 47 Texaco engineers looked for a new Three-string Two-string ■ method and worked with Kniffin to design Three- and two- string completions. lightweight cementing techniques that Applying light- allowed elimination of the intermediate weight mud and string. Lighter fluids permitted cementing Surface cement, Texaco the production string in one stage or, if very saved about 10 to 15% on each comple- long, in two stages. Stage 2 tion by deleting the Taking this approach required that Texaco cement intermediate string. accept the risk of lost circulation and water entry during drilling. Managing this risk, however, or even repairing damage done by water entry, is less costly than setting inter- Intermediate mediate casing. Texaco has used the proce- dure on select projects since 1992, saving 10 to 15% on each well. “It allows us to drill in places where we could not have afforded to drill otherwise,” said Phil Basham. “Every nickel saved got reinvested in a new well. That’s the kind of benefit we’re after.” Stage 1 cement Shell Western E&P: High-Pressure Production Coiled Tubing South Texas presents Shell Western E&P Inc. with some of the company’s most challenging gas wells. They are deep, hot, geopres- sured and sometimes sour. In the Rio Grande Valley, Shell produces 450 million cubic ft of gas and condensate per day from butions to fracture design have increased hydraulic fracturing. In this fracturing tech- about 350 wells. The main technical chal- Dowell’s share of jobs and enhanced effi- nique, the bottom zone is fractured first, lenge is beating the decline curve of the ciency for Dowell and productivity for then the interval is filled with sand to isolate wells—the fall in productivity over time—by Shell. His contribution to an innovative it, and the zone above is fractured. The sec- lowering the cost of production and produc- application of coiled tubing for workovers ond zone is then filled with sand, and the ing hydrocarbons as fast as possible. helped save Shell $1 million in 1994 and zone above that is treated, and so on up the Duncan Newlands, Shell’s Houston- expanded Dowell’s coiled tubing services hole. After the final fracture, the column of based DESC engineer, addresses this chal- in the region.5 sand, which may reach a thickness greater lenge by splitting his time between fracture Coiled tubing is used to clean out sand than 1000 ft [305 m], must be removed to work and coiled tubing services. His contri- plugs inserted during multistage massive commingle production from all the zones.

Getting the Most from Perfs

To minimize entrance effects and maximize ■Electronics Technician fracture conductivity, Kniffin and a team of Walter Limpias with gel Texaco engineers are trying a combination of pumped on a typical five techniques: Kern River frac job. • Larger-diameter perforations. Historically, holes were commonly of small diameter—typically 0.35 in. [0.9 cm] or smaller. Larger-diameter perforations—0.5-in. [1.3 cm] and larger—are thought to result in a more direct path from perf to fracture.

48 Oilfield Review With wellhead pressures sometimes at a depth of 12,000 ft [3658 m]. Because approaching 10,000 psi, snubbing units only 30 ft can be “snubbed” at a time, were used to remove sand, since conven- removal of the column of sand can take 7 to tional coiled tubing units can accommodate 12 days. wellhead pressure only up to 3500 psi. A A team of Shell and Dowell engineers snubbing unit is a combination of pressure investigated the practicality of adapting control and pipe handling equipment existing coiled tubing and surface equip- (below). The equipment jacks pipe through ment to cope with the high pressures. They the pressure control equipment 30 ft [9 m] found that conventionally available 11/4- at a time. When at the required depth, gel is inch, thick-walled coiled tubing provided pumped down the pipe to circulate sand to the best of all possible properties: strong the surface. The typical south Texas well has enough to safely endure the wellhead and a producing interval of at least 200 ft [60 m], downhole pressures, large enough to accommodate pump rates for efficient cleanout, and having an acceptable fatigue life, given the high operating pressure. Two pieces of equipment had to be adapted. First, the high pressure at the wellhead made buckling of tubing at the stripper a concern. To combat this, an antibuck- ling guide was utilized to provide lateral support and minimize the distance between the stripper and chains that drive the tubing in and out of the injector. Second, a 15,000-psi blowout preventer and stripper were built to improve the economics, safety and speed of the coiled tubing job. Yard tests at operating pressures showed the new equipment could perform several cleanouts before a string of coiled tubing would have to be retired to conventional work. Since 1994, the technology has been used

Rick Prudhome to perform more than 75 cleanouts, each

■Removing sand with a snubbing unit (top) and a coiled tubing unit with new high-pres- 5. Van Adrichem WP, Gordon DG and Newlands DJ: sure surface control equipment. The snubbing unit is about 70 ft [21 m] high, and “Development and Utilization of a Coiled Tubing requires personnel working at the top, which is a significant safety risk. Removal of sand Equipment Package for Work in High Pressure Wells,” in a south Texas well takes about one week with a snubbing unit but can be performed paper OTC 7874, presented at the 27th Annual OTC with a coiled tubing unit in fewer than three days, and at a lower safety risk. Meeting, Houston, Texas, USA, May 1-4, 1995.

• Tighter phasing of perforations. Decreasing the • Maximized pad fluid viscosity. A pad is the first 1. For more on near-wellbore tortuosity and proppant slugs: phase angle of perforations maximizes the fluid pumped during hydraulic fracturing, and Cleary MP, Johnson DE, Kogsbøll H-H, Owens KA, Perry KF, de Pater CJ, Stachel A, Schmidt H and Tambini M: “Field likelihood of a perforation aligning parallel to generally does not contain proppant (previous Implementation of Proppant Slugs to Avoid Premature the fracture plane. At the ideal alignment, frac- page, bottom). The more viscous the fluid, the Screen-Out of Hydraulic Fractures with Adequate Proppant Concentration,” paper SPE 25892, presented at the SPE tures tend not to split into multiple branches, wider the fracture; it also makes the job more Rocky Mountain Regional/Low Permeability Reservoirs minimizing the number of restrictions that lead costly because of the requirement for added Symposium, Denver, Colorado, USA, April 12-14, 1993. 2. Stadulis JM: “Development of a Completion Design to Con- to screenout. horsepower and for breakers, chemicals that trol Screenouts Caused by Multiple Near-Wellbore Frac- tures,” paper SPE 29549, presented at the SPE Rocky • Proppant slugging. This process involves early reduce viscosity after pumping. Optimal viscos- Mountain Regional/Low-Permeability Reservoirs Sympo- pumping of small, intermittent volumes of prop- ity balances added cost against higher fracture sium, Denver, Colorado, USA, March 20-22, 1995. pant slurry (slugs) with progressively higher conductivity. densities of proppant.1 These slugs are thought • Limiting the height of the perforated interval, to plug off minor fractures, diverting more of called point-source perforating.2 Perforating the proppant to the major fractures, improving only a limited height, usually in the middle of their conductivity. the interval of interest, reduces the number of multiple fractures and increases the likelihood of them coalescing into fewer, larger fractures.

Summer 1995 49 taking 1 to 3 days to complete at about half Newlands to concentrate more on process boost production in wells already consid- the cost of a conventional snubbing unit. reengineering and optimizing fracture design. ered to be doing their best. Finding candi- There has been interest in expanding the At Texaco, prior to the nationwide alliance, dates for new technology, like the south technique to fields in the Gulf of Mexico the seven DESC engineers in Texaco offices Texas wells cleaned with high-pressure and the Middle East. provided solutions specific to the geo- coiled tubing, will build business for Dowell “Duncan’s main contribution in this pro- graphic area served by those offices. With while cutting cost and boosting productivity ject was as an enabler,” said Bill Taylor, well the formation of the nationwide alliance, for operating companies. servicing team leader for Shell. “Because there is a trend away from using the DESC New technology also includes new tools he’s immersed in our business, he knows engineer as only a local solution. Now 11 for candidate recognition. To this end, sev- our needs, and is able to bring together the Texaco DESC engineers pool knowledge eral reservoir engineering analysis programs key Dowell experts to meet the challenge. with their respective local Texaco col- have recently been added to the DESC engi- You walk around this office and you hear a leagues to spread best practices throughout neer’s toolbox. These tools let the DESC lot of ‘Duncan said —.’ That means his fresh the organization. “Not only do we want to engineer evaluate the current condition and perspective is bringing us results.” drive out redundancy and boost production potential of more wells with greater speed in Kern River,” said John Baltz of Texaco, and ease. This ultimately leads to faster What Comes Next? “we want to align on process and process identification of opportunities and earlier Once a DESC engineer is installed in an analysis everywhere. That is a driver of our enhancement of well productivity. operating company, gains the client’s trust financial success.” “To make this program grow productively, and knowledge of the client’s needs, works Both Texaco and Shell have seen the role the most important element is encouraging to continuously reduce cost and build proof the DESC engineers expand as they prove the Dowell engineer to focus on client ductivity, what comes next? their expertise, and as the operating compa- objectives,” said Jerry Richards, Dowell vice It varies with the company. For some, like nies gain trust to delegate more work. This president. “I can’t overemphasize the impor- Shell Western, it means adding another means the definition of candidate recogni- tance of that. It is the key to growing our DESC engineer. In the Houston office, a sec- tion widens to encompass not only obvious business and the customer’s business, which ond DESC engineer will focus exclusively underproducing wells but to include appli- is the purpose of the DESC program.” on candidate recognition, allowing Duncan cation of new technology and techniques to —JK

Who they are

Mitch Kniffin Duncan Newlands Fred Mueller • Texaco DESC engineer, Midland, • Shell DESC engineer, Houston, Texas, • Texaco DESC engineer, Bakersfield, Texas, 1992; Denver, Colorado, since since May 1994. California, since September 1993. October 1994. • Two years as a sales engineer in • Five positions in marketing, engineer- • Seven postings in sales, engineering Houston, preceded by two years as a ing and sales, preceded by assign- and management, in North Dakota, training instructor at Dowell’s ments in three field locations in south Kansas, Louisiana, Oklahoma and Kellyville (Oklahoma) Training Center, Texas and the North American mid- Texas. and three field assignments in the continent. • Hired with Dowell in Gainesville, Rocky Mountains. • Hired with Dowell in Bryan, Texas, Texas, 1979. • Hired with Dowell in Gillette, 1980. • BS degree in chemistry, Kansas State Wyoming, 1987. • BS degree in engineering technology, University, 1979. • BS degree in geology and BS degree in Texas A&M University, 1980. petroleum engineering, Texas A&M University, 1986.

50 Oilfield Review