ECS Elemental Capture Spectroscopy Sonde
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ECS Elemental Capture Spectroscopy Sonde Fast, accurate lithology evaluation Applications Challenge: Fast petrophysical answers The 4.5-m [15-ft] ECS sonde emits high-energy n Identify carbonate, gypsum, from elemental concentration logging neutrons into the formation, and a detector and anhydrite; quartz, feldspar, Formation parameters and formation- measures the gamma rays emitted by the reac- tions of neutrons with elements in the formation. and mica; pyrite, siderite, coal, zonation levels can be defined by skilled and salt fractions for complex interpreters or by referring to an estab- reservoir analysis lished database. There are times though n Estimate mineralogy-based when neither is available. permeability Geoscientists have long desired to provide a petrophysical answer from n Determine well-to-well corre- elemental concentration logging— lation from geochemical comprising at least porosity and water stratigraphy saturation—in real time or within a few n Determine sigma matrix for hours after logging a well. This informa- cased hole and openhole tion is essential to making decisions on sigma saturation analysis running casing and completing wells. n Delineate coalbed methane n Estimate producibility and in Solution: ECS Elemental Capture situ reserves Spectroscopy sonde Electronics Pulsed neutron spectroscopy logging cartridge Benefits tools have been used in openhole for- mation evaluation since the late 1970s n Clay fraction values, independ- to measure elemental concentrations ent of gamma ray, spontaneous in rocks and estimate the major matrix potential, and density-neutron properties from them. The early tools, n Advanced, integrated petro- however, were not widely used because physical evaluation and they were physically long, costly to analysis operate, and the data interpretation n Matrix density and neutron was complex. values for improved porosity The ECS sonde, which is a short, values simple-to-use logging tool, measures n Robust petrophysical evalua- and processes gamma ray spectra, or tion with minimal user inputs the number of gamma rays received by in sand-shale reservoirs the detector at specific energy levels. These measurements allow for more Am-Be source n Enhanced completion and accurately defining the clay content, drilling fluid recommendations mineralogy, and matrix properties of n Quantitative lithology for each potential zone. rock properties modeling and pore pressure prediction Detector from seismic data Boron sleeve Features n Supports most geoscience disciplines Electronics n Well-to-well data correlation for exploration and develop- Dewar flask ment projects n Quantitative lithology for Heat sink accurate determination of porosity, fluid saturation, and k-lambda permeability n Lithology for rock-properties modeling, seismic calibration, and pore-pressure prediction from velocity data n Better mechanical properties for fracture design and stimu- lation fluid selection Results: Better measurements for DecisionXpress* output for a log of a siliciclastic sequence. A light gray mask indicates log intervals in better interpretation which the input data are of poor quality because of hole conditions or other problems. The porosity, per- Using the neutron-induced capture meability, and fluid saturations are summed and averaged over the pay interval using cutoffs on perme- ability and water cut selected by the user. These can also be presented in a table. Quality-control flags gamma ray spectroscopy principle, the in the far right track indicate the interpretation description for lithology (L), porosity (P), permeability (K), ECS sonde determines relative elemen- saturation (S), and relative permeability (R). Green indicates favorable interpretation, yellow means a tal yields by measuring the gamma rays moderately favorable interpretation, and red reflects an unfavorable interpretation. The shale interval above X,240 ft is largely affected by poor hole conditions. produced when neutrons bombard the formation and lose energy as they are scattered, primarily by hydrogen. Porosity The primary formation elements Siderite measured by the ECS sonde in open Clay-Bound Water Anhydrite and cased holes are the most com- Capillary-Bound Water Pyrite Water monly occurring elements: silicon, iron, Free Water Carbonate Pay Hydrocarbon calcium, sulfur, titanium, gadolinium, Water Hydrocarbon Quartz/ Feldspar/ Mica Cable DecisionXpress Water Cut chlorine, barium, and hydrogen. Tension Mineralogy Hydrocarbon 10Moved Hydrocarbon Clay 1lbf 5,000 Gamma Ray Flow Profile Intrinsic Permeability Porosity Volume LPKSR Measuring yields with the ECS sonde MD, ft 0 gAPI 200 0 1 10,000mD 0.1 50% 0 0% 100 Lithologic fractions of total clay, total carbonate, and QFM (quartz, feldspar, X,250 and mica) are derived from the concen- trations of silicon, calcium, and iron. Matrix density is calculated from silicon, calcium, iron, and sulfur, and it is com- bined with the measured bulk density to derive an accurate total porosity. In a similar way, the elemental concentra- X,300 tions of silicon, calcium, and iron are used to correct the neutron log for rock matrix effects, thereby yielding neutron porosity that is significantly closer to total porosity. SpectroLith* lithology processing of spectra from the ECS sonde is based X,350 on a technique in which measurements of silicon, calcium, and iron are used to produce an estimation of clay as accu- rate as that derived from a measure- Typical gamma ray spectrum from the ECS sonde in a siliciclastic environment that has no calcium or ment of aluminum. sulfur. The thermal neutron capture gamma rays are shown divided into the contributions of the different Carbonate concentrations are deter- elements present. Gamma rays from inelastic neutron reactions are also present, but are not used quanti- mined from the calcium concentration tatively. The capture yields of iron (Fe) and calcium (Ca) include small signals from aluminum and sodium. This contamination is taken into account during further processing. log with exceptional accuracy. The anhydrite volume is determined from the calcium and sulfur logs; thus, the remainder of the formation is com- posed of QFM. SpectroLith processing is used to compute pyrite, siderite, coal, and salt. Gd Number of H gamma rays detected, Si Fe counts/s Cl Inelastic 0 50 100 150 200 250 Gamma ray energy, measurement bin number Complementary technologies Data from the Platform Express tool and the ECS sonde are integrated to determine mineralogy. This pres- The DecisionXpress petrophysical eval- entation shows borehole and depth information, red net pay flags, and yellow net reservoir flags in the uation system integrates data from the depth track. Track 1 shows lithology from the Platform Express tool. Perforations in four zones and the flow profile are shown in Track 2. However, the water cut information in Track 3 reveals a zone near X,675 ft that ECS sonde and the Platform Express* ultimately produced water. Fluid interpretations in Track 4 suggest that the best oil potential exists just integrated wireline logging tool to pro- below X,600 ft and around X,700 ft. The dominant minerals, shown in Track 5, include quartz, feldspar and vide rapid data visualization and repro- mica (yellow), and clay (gray), with minor amounts of carbonate minerals (blue). Summarized in quality- control Track 6 are lithology (L), porosity (P), permeability (K), saturation (S), and relative permeability (R); cessing capabilities at the wellsite or in where green reflects a favorable interpretation, yellow a moderately favorable interpretation, and red an a client’s office. This combination pro- unfavorable interpretation. Track 8 shows hydrocarbon volumes. vides a robust petrophysical evaluation with minimal user inputs in sand-shale reservoirs for planning of coring and Net Pay Porosity sampling operations; decisions for Net Reservoi r casing, drilling ahead, or sidetracking; Clay-Bound Water Siderite Mudcake Wa te r Capillary-Bound Wa te r Pyrite and the design of completion strategies. Perforated Intervals Wa shout Accurate measurement of relative Hydrocarbon Free Wa te r Carbonate Bit Size elemental yields with the ECS sonde, Wa te r Wa ter Cut Hydrocarbon Quartz/ Feldspar/ Mica 61in. 6 DecisionXpress 10 coupled with SpectroLith processing Caliper Mineralogy Hydrocarbon Moved Hydrocarbon Clay Hydrocarbon Intrinsi c 61in. 6 and DecisionXpress petrophysical eval- Gamma Ray Flow Profile Permeability Porosity Vo lume S w L P K S R uation, can help improve production, MD, ft 0 gAPI 150 01 10,000 mD 0.1 50 % 00% 100 100 % 0 reduce costs, and minimize risks. Rapid evaluation of complex lithologies A Middle East operator drilling with X,600 two rigs needed rapid petrophysical wellsite analysis to help minimize the impacts of geological uncertainty and abrupt changes in formation-water resistivity on operations. Prospective sandstones tended to be thinly bedded and varied widely in grain size. A complex mineralogy, including glauconite, complicated log interpretation. The operator selected the DecisionXpress service because X,650 it integrates data from the Platform Express tool and the ECS sonde to determine mineralogy. This combina- tion also provides a continuous matrix density measurement that can be used in subsequent log processing. The ECS data helped to identify zones contain- ing significant amounts of calcite. This was not possible using standard logs, which are affected by barite in the X,700 drilling mud. Prompt, robust interpretations based on the DecisionXpress