Gas-Handling Devices Boost Mississippi Lime Production by Diego A
ARTIFICIAL LIFT & PRODUCTION ALTERNATIVESMay/June 2014
Technology and Services for Oil & Gas Operations
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REPORT FROM THE FIELD
Gas-Handling Devices Boost Mississippi Lime Production By Diego A. Narvaez & Jan Cox, Schlumberger
ESPs with added technology can successfully provide artificial lift in this play, despite its water challenges.
rtificial lift is giving the similar to shales. It is highly fractured cost-effective from a drilling perspec- Mississippi Lime play a new and has a complex and varied geol- tive. Thickness of the play ranges lease on life, allowing pro- ogy of layered chats, cherts, dolomites from 300 feet to 500 feet as it moves duction companies to tap a wealth and limestones that change vertically to the east, with the pay zone rang- ofA resources that would otherwise be and horizontally. Reservoir evalua- ing from 100 to 300 feet in thickness. inaccessible because of the formation’s tion methods using petrophysical and Initial production rates can be as high high water content. Spanning more seismic data to characterize faults, as 5,000 barrels per day in the core than 17 million acres across northern fractures, porosity and thickness have operating area of north Oklahoma. Oklahoma and southwestern Kansas, proved useful for maximizing pro- Recovery potential declines as the the oil-rich Mississippi Lime has been duction—which is a multiphase flow play moves into Kansas. producing for more than 50 years consisting of oil, gas and water—and Flow rates are generally higher, from vertical wells. Today, operators placing closely-spaced wells. and production declines slower, than are applying horizontal drilling and Unlike other prolific unconven- those in other unconventional North hydraulic fracturing to recover the re- tional plays, such as the Bakken and American plays. Wells also tend to be maining hydrocarbons, estimated to the Eagle Ford, the Mississippi Lime cooler, 130 to 160 F, compared to an range from 5.4 to 5.9 billion barrels of does not demand a high degree of ad- average 260 F in other formations be- oil equivalent. Of the play’s more than vanced drilling and completion tech- cause of the shallow geology. Drilling 32,000 wells, about 2,500 are hori- nologies. Wells are shallow—ranging and completion costs average $3 mil- zontal, and the number is growing. from 3,000 to 7,000 feet deep—and lion to $3.5 million per well, com- Although not a shale play, the un- laterals are relatively short, typically pared to $6 million to $8 million in conventional carbonate formation is around 5,000 feet, making them other formations.
On the Cover: Engineers install an ESP motor as part of a downhole system.
32 Upstream Pumping Solutions • Reprinted from May/June 2014 ARTIFICIAL LIFT & PRODUCTION ALTERNATIVES
construction phase so that the wells Lifting Water, Gas can support the operator’s production & Sand goals. For example, typically an ESP Mississippi Lime wells produce as or a sucker rod pump is set in the ver- much as 98 percent water in some tical section of the well, right above cases, a phenomenon that impacts the kick-off point (KOP), because of overall project economics. The higher restrictions—such as a smaller diam- water cut results in higher lifting costs eter above the KOP, high dogleg se- per barrel and drives the operation verity (DLS) or absence of a tangent companies’ objective to maximize or low DLS section to set the ESP. production from day one. To achieve The production of the proppant or maximum production, operators rely sand used in hydraulic fracturing can on artificial lift methods—such as sometimes determine the artificial sucker rod pumps, electric submer lift method that will be used because, sible pumps (ESPs) and gas lift. even if the well has a tangent section The steep production decline— in which the ESP can operate, the risk often further aggravated by high sand of having the system stuck in the well concentration and high gas content is too high. with the produced fluids—poses The gas volume fraction (GVF) at serious challenges to the operation intake conditions is high in this play, of wells in unconventional plays. especially at low pump intake pres- Unfortunately, this is not always evi- sure. Gas can negatively impact ESP dent during the first stages of devel- performance and run life by causing opment and can lead to discouraging rapid changes in density that compro- run times when using conventional mise the hydraulic lift capacity of the artificial lift systems. However, opera- pump, sometimes causing gas-lock. tors and service companies are quickly The nature of the long, horizontal learning that a successful production sections of unconventional wells can development phase in unconvention- also lead to gas slugs, which increase al formations requires fit-for-purpose the GVF even more. artificial lift design, equipment con- Standard ESPs rely on centrifugal figuration, measurements, real-time force to transfer energy to the liquid control and operating procedures. and gas mixture. However, the liquid This approach often implies a transi- and gas can separate, even with a free tional artificial lift method, such as an gas content of just 10 to 20 percent in ESP, initially, followed by a lower-rate the pump, resulting in a less efficient artificial lift system, such as a gas lift or transfer of energy. If enough gas accu- sucker rod pump, for the late stage of mulates, the pump will gas-lock and the well life cycle. prevent fluid movement. Within the continuous improve- ESP systems equipped with ment process, operators in uncon- an advanced gas-handler (AGH) ventional plays work with service device can mitigate these limita- companies and understand that tions and improve overall lift ef- these operational challenges must ficiency by reducing the degrada- be considered in the well design and tion effects of centrifugal pumps and maintaining the higher gas-to- The multiphase helico-axial pump system can liquid ratio in the tubing string. The operate at lower intake pressures with GVF in the AGH can tolerate multiphase mix- pump up to 75 percent, delivering incremental production and improved reserve recovery. tures up to 45 percent free gas and is
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installed as a component of the ESP in the Mississippi Lime. However, and maximize the effectiveness of the string, right below the pump. because of the additional challenges artificial lift in line with the operators’ The AGH reduces vapor bubble of unconventional plays and the op- goals. sizes and changes the gas-bubble dis- erators’ requirement to accelerate the New technologies are rejuvenating tribution, homogenizing the gas-liq- production of horizontal wells, sucker old formations. As operators look to uid mixture so that it acts like a single- rod pumps are not always the best op- tap the tremendous potential of the phase fluid before entering the pump. tion for operation across the whole Mississippi Lime, they are relying on By processing and conditioning the well life cycle. advanced artificial lift methods to multiphase gas and liquid mixture For an increasing number of appli- boost flow rates and overcome the before delivering it to the pump, the cations, operators are installing ESP challenges of multiphase production, device allows further drawdown, im- systems early in the life of the well, ensuring the long-term viability of proves pump uptime and accelerates sometimes immediately after drilling this important and prolific play. production. out the fracture plugs. ESP systems A more robust multiphase gas- are used as a transitional artificial lift handling device is required with method until they are replaced with a Diego A. Narvaez is North America higher GVF. A specially designed, sucker rod pump for the late life cycle technical manager, Artificial Lift, multiphase helico-axial pump safely of the well. Upon withdrawal from for Schlumberger. He has 23 years’ handles mixtures of up to 75 percent the well, the downhole components experience in the oil and gas industry working for an operator and service of the ESP are inspected and repaired free gas, enabling the ESP to operate company. Narvaez has held a number at a lower intake pressure without as needed, then transferred to the of technical roles in several interna- gas-locking. Depending on the appli- next well on transitional artificial lift. tional assignments with Schlumberger cation, the system can be installed in Well cleanout of long horizontal since 1996. He has a Bachelor of conjunction with a standard intake or sections is a challenging task, and of- Science degree in mechanical engineer- with a gas separator. ten, the ESP is used to complete the ing from Escuela Politécnica Nacional ESP technology has been effective cleanout operation. However, the and has also completed an MBA from in addressing these challenges when high, sustained production of abrasive the University of Phoenix. Narvaez holds several patents on technology configured with the proper technol- solids in the well can shorten the run inventions related to artificial lift. ogy and adequate operational prac- life of the pumps. When the volume tices. A Mississippi Lime operator re- of sand and other foreign materials is Jan Cox is stimulation domain cently pulled an ESP after 16 months too large to be transported with the manager, North America Land of operation. The operator success- fluid stream, the pumps, and some- Central, for Schlumberger. With more fully managed a steep production de- times several joints of tubing above, than 20 years of industry experience cline from 5,000 barrels per day (bpd) become completely plugged shortly from the North Slope of Alaska to the to 500 bpd with the same ESP system after the installation. Western Desert of Egypt, Cox has enjoyed many technical assignments before the workover rig returned to Fit-for-purpose pumps designed with Schlumberger. Currently, Cox the well. with abrasion-resistant radial bear- is working in Oklahoma City with ings and stage materials, coatings and Mid-Continent unconventional plays, Extended Pump Life compression construction compo- supporting a wide range of stimulation As the most common technique of nents are successfully extending the and completion projects with a team artificial lift in North America, sucker run life of ESP systems in this envi- of Schlumberger’s most experienced rod pumping is often the method of ronment, as long as the sand can be technical engineers and geoscientists. choice. Operators are familiar with carried with the produced fluid. Real- © Copyright 2014 Cahaba Media Group, Inc. All rights the pumps’ operation, which can be time surveillance and optimization reserved. Permission granted by publisher to Schlumberger to a visible and efficient artificial lift op- service and appropriate operational reproduce and distribute this excerpt in any medium and on multiple occasions, provided that this copyright statement tion for shallow wells, similar to those procedures complement the system appears on the reproduced materials.
34 Upstream Pumping Solutions • Reprinted from May/June 2014