This paper deals with the case of shaly sand formation as a low resistivity pay zone. An onshore gas field hereafter called the r fieldreal name not revealed is in the southeast coast of tanzania which includes a tertiary aged shaly sand formation sandshale sequences. The occurrence of shale in reservoir rocks can result in erroneous values. Shaly sand evaluation is a complex task and a good geological. Shaly sand formation evaluation from logs of the skrugard well, southwestern barents sea, norway by marco shaban lutome supervisor. A modified approach for volumetric evaluation of shaly sand. Formation evaluation is consequently based mostly on logs. Review of existing shalysand models and introduction of a. Shaly sand formation evaluation using a single membrane. Hari kumar, ongc summary present paper is a relook at the oil industry practices in making use of the simandoux and indonesian shaly. The shale volume is about 9 percent and formation water resistivity for virgin zone is 0. In potential shalegas basins, due to limited data availability, volumetric evaluation of shaly sand formations is a challenging task for researchers, as well as for exploration and production companies, with the use of conventional well logs. Pdf shales in the reservoir causes complications for the.
An integrated formation evaluation approach for maximizing the value. Evaluation of gas hydrate saturation by effective medium theory in shaly sands. This model was modified to include a, n and m constants. Accuracy of shaly sand formation evaluation saudi aramco. The determination of reservoir quality and formation evaluation processes largely. Cation exchange capacity q v is a key parameter in resistivitybased water saturation models of shaly sand reservoirs, and the accuracy of q v calculation is crucial to the prediction of saturations of oil and gas.
The shaly sand formation had alternating lowporosity, gasfilled zones and verylowporosity zones. The sand percentage here is generally less than 30%. Evaluation of low resistivity laminated shaly sand reservoirs. Pdf hydrocarbon saturation assessment of thick shaly sand. Typically, the formation lithology included minerals which were termed clay or clay minerals. A simplified shalysand model to provide qualitative if not.
To alleviate the problem of overestimating water saturation by archie many shaly sand interpretation models have been developed that accommodate the. Pdf integrated petrophysical evaluation of a heterogeneous. Silt contents will reduce the permeability and increase the water saturation. Petrophysical analysis of shaly sand gas reservoir of titas gas field using well logs. Lithology investigation of shaly sand reservoir by using wire line. Evaluation of the hydrocarbon potential in lowsalinity.
Formation evaluation for thin bed shaly sand reservoirs russian. A novel process and methodology in deterministic formation evaluation is provided. Analysis of shaly sand reservoir rocks in the eastern niger. Therefore, the effects of clay on porosity and resistivity logs were not accurately incorporated in shaly sands formation evaluation. However, only two sections of two wells from these four had core data available. The formation evaluation results can accurately quantify formation attributes, such as clayvolume, clayboundwater, effectiveporosity and water saturation in shaly sands. Sharma center for petroleum and geosystems engineering, the university of texas at austin, cpe 2. Formation evaluation using wireline logs is an appropriate means to obtain petrophysical properties for the r field with well rx in the target. The formation was penetrated by an exploration well rx wherein no core was acquired, and there is no layerwise published data of the petrophysical properties of the r field in the existing. Petrophysical evaluation of shaly sand reservoirs in palougefal.
Petrophysical interpretation in shaly sand formation of a. Laminated shaly sand reservoirs an interpretation model. Each of these can furnish a significantly different reservoir evaluation. Advances in coring and core analysis for reservoir formation evaluation 3 sedimentology the study of processes by which sedimentary rocks are formed, e. Subsurface and petrophysical studies of shalysand reservoir. For a symmetric distribution, this will equal the p50 value. However, in shaly formation this approach misleads the results by overestimating the water saturation value due to extra conductivity contribution from clays or shales. Analysis of shaly sand reservoir rocks in the eastern niger delta basin using geophysical well logs. This paper is intended to provide a better understanding of volumetric evaluation in unconventional shaly sand formations. Multicomponent induction resistivity logs allow differentiation of horizontal and vertical resistivity.
Sandor, shell international exploration and production b. The central role of qv and formation water salinity in the evaluation of shaly formations the log analyst, julyaugust 1979. The presence of clay minerals and shale laminations strongly affects the physical properties of the reservoir rock and induce significant effects on the response of most logging tools. This course tackles the important and nontrivial problem of practical formation evaluation in shaly sand provinces.
About the course this course tackles the important and nontrivial problem of practical formation evaluation in shaly sand provinces. For a considerable time, shaly sand formation evaluation could not accurately quantify clay from standard well logs. Pnge 735 advance formation evaluation course description. The agbada formation consists of alternating sand and shales representing sediments of the transitional environment comprising the lower delta plain mangrove swamps, floodplain, and marsh and the coastal barrier and fluviomarine realms. Subject to many uncertain parameters is the accurate determination of formation porosity and fluid saturation in shaly sand, which are all induced by the existence of shale in pay formation. Analysis of shaly sand reservoir rocks in the eastern niger delta. This leads to large uncertainties in the apparent sand resistivity even for. In any petroleum province in the world where there are sandshale sequences, the geologist, engineer or log analyst confronts toe shaly sand problem. Tool axis perpendicular to the formation in this case measurement axis of the tool is parallel to the formation layers and hence if vertical resolution of the tool is of the extent to include alternations of sand shale layers, the recorded resistivity will be equivalent to the shale.
The model was a result based on laboratory studies performed on a physical reservoir model composed of artificial sand and clay in the laboratories of the. The shaly sand effect formation factor f was not intrinsic rock property, but instead was seen to vary with water salinity due to clay x called extra conductivity the problem. This petroknowledge training course provides the participant with an intensive training on the concepts of the petrophysical interpretation and well logging. The conventional resistivity in a laminated shaly sand formation for the sand resistivity r sd of 20. A method of shaly sand correction for estimating gas. Electrical properties, petrophysics and formation evaluation. Shaly sand petrophysics training course petroskills aps. Vsh rsh from log analysis indonesia eqn formulated for evaluation of. This study presents an integrated petrophysical evaluation for nahr umr reservoir by highlighting a practical trustworthy approach petrophysical model for nahr umr reservoir in subba oil field depending on available data. In logging analysis, shalysand formation evaluation estimates totalporosity. The shaly sand effect formation factor f was not intrinsic rock property, but. Modeling of porosity and permeability for hydrocarbon.
The assigned formation for evaluation was the 3rd bone spring sitting immediately above the wolfcamp and located in the leonardian period. On the application of simandoux and indonesian shaly sand resistivity interpretation models in low and high rw regimes k. Petrophysical analysis of the 3rd bone spring formation. Examples with an exercise part sandstone reservoir, shaly sand interpretation, complex mineralogy of a carbonate reservoir help to understand the different methods and algorithms. In lo g interpretation of shaly sand is used matrix densit y of quartz d. Pdf analysis of shaly sand reservoir rocks in the eastern niger. Both low salinity and shaliness reduce the resistivity contrast between oil and water. In the laminated shaly sand sequences, the shaly part of these layers is more conductive than the sandy part which in turn yields incorrect estimation of the hydrocarbon in laminated shaly sand layers. Analysis of shaly sand reservoir rocks in the eastern niger delta basin using geophysical. Worthington p f 1985 the evolution of shaly sand concepts. In logging analysis, shalysand formation evaluation estimates totalporosity, shale and quartz in shalequartz lithologydescription or clay and sand in claysand lithologydescription, effectiveporosity and watersaturation. Cation exchange capacity qv estimation in shaly sand. Successful testing in some exploration wells, which flowed gas and condensate from gumai reservoir, opened the opportunity to explore the new play potential in betara complex.
Overview well log definition and its importance fundamentals of qualitative and quantitative log interpretation formation evaluation with well logs processing and interpretation of well log data conclusion 3. Hari kumar, ongc summary present paper is a relook at the oil industry practices in making use of the simandoux and indonesian shaly sand resistivity interpretation models for formation evaluation. Formation evaluation from well logs in laminated shaly sands has often suffered from lack of proper models, and in many cases led to underestimation of. Fundamentals of formation evaluation training course.
Jan 30, 2007 typically, the formation lithology included minerals which were termed clay or clay minerals. Shaly sand evaluation is a complex task and a good geological and local knowledge is important. The 3rd bone spring formation is predominantly shaly sand with intermittently interbedded carbonate layers. In logging analysis, shaly sand formation evaluation estimates totalporosity, shale and quartz in shalequartz lithologydescription or clay and sand in clay sand lithologydescription, effectiveporosity and watersaturation. A new equation is derived that directly relates shaly sand conductivity to the membrane potential. Subject are the fundamental techniques of well loggingborehole geophysics and the interpretation of measured data formation evaluation. Water saturation models for shaly sand reservoirs presence of shale in the formation has been considered as a very disturbing factor and shown severe effects on petrophysical properties due to reduction in effective porosity, total porosity and permeability of the reservoir ruhovets and fertl, 1982. Pdf formation evaluation of x7 field in the niger delta.
Pdf petrophysical analysis of shaly sand gas reservoir of. Integrated petrophysical evaluation applied to the. Petrophysical evaluation, shaly sand reservoirs, density neutron logging, palougefal oil. Advanced formation evaluation in sandstone reservoirs. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. Print to pdf email progression map browse sessions in this discipline. In this study, a theoretical expression of q v in terms of shaly sand permeability k shalysand, total porosity. Of course, the hydrocarbon inplace is obtainable once porosity and water contents are estimated in the formation.
R ar o w m 1 where r o is the formation resistivity of watersaturated sediment, r w. Summary formation evaluation from well logs in laminated shaly sands has often suffered from lack of proper. The relationship between the resistivity index and the water saturation is also expressed in terms of a single membrane potential measurement. Worthington p f 1985 the evolution of shaly sand concepts in reservoir from pte 461 at university of southern california. As a means of investigating this unsatisfactory state of affairs, the development of thinking about the shaly sand problem has been mapped up to the present day. Statoil for providing financial support during the entire period of my study in norway and in tanzania. The shaly sand problem is really a question of identifying, from logs, the degree to which the presence of clay degrades reservoir quality, because clay affects both porosity and. Evaluation of laminated shaly sand sequences in ahwaz oil. Geological survey scientific investigations report 20065121, 10 p.
Petrophysical evaluation of shaly sand reservoirs in. The petrophysical work flow that is presented through the paper can be applied to other mature, complex shaly sand reservoir for formation evaluation. Yet, no one method predominates within the industry. The aim of this research was to build a comprehensive interpretation algorithm to evaluate the shalysand reservoir. A modified approach for volumetric evaluation of shaly. Petrophysical models and techniques for shalysand formation. Petrophysical interpretation in shaly sand formation of a gas field in. Basin and covers approximately 10,000 square miles. On the application of simandoux and indonesian shaly sand.
Thin laminated shalysand would require high resolution imaging tools to quantify. Us7168310b2 accuracy of shaly sand formation evaluation. May 20, 2019 the conventional resistivity measurements are generally influenced by the conductive formation. Mar 28, 2019 evaluation of gas hydrate saturation by effective medium theory in shaly sands. The evolution of shalysand concepts in reservoir evaluation. This paper presents a new model for shaly sand formation permeability evaluation within the transition based on the application of the dual water model formation parameters such as. Shaly sand reservoirs impact on porosity and water. Petrophysical evaluation of shaly sand reservoirs in palouge. The clays, when saturated with formation water, may adsorb water and form immobile water film on the surface of sand grains hill et al1956, waxman and smits 1968, clavier et al1984, juhasz 1979. Pdf advances in coring and core analysis for reservoir. Toby darling, in well logging and formation evaluation, 2005. The conventional resistivity in a laminated shaly sand formation for the sand resistivity rsd of. Comparing the results of different shalysand evaluation methods is dif.
The new spectroscopy system unique ly provided the operator with a standalone petrophysical volumetric inter. Statoil for providing financial support during the entire period of. An integration and evaluation of gas while drilling data initiated with the objective to. Simandoux 1963 developed a model for estimating water saturation in shaly sand formation. Advanced methods for interpreting well logs, shaly sand analysis, and production logging methods.
Tool enables complete casedhole formation evaluation. Compared with the porous clean sand sample, actual shaly sand usually has clays that adhere to or cover on the grains figure 2. Petrophysical evaluation of these reservoirs type is needed. An integrated formation evaluation approach for maximizing. Formation evaluation and well log correlation swapnil pal imt geological technology indian institute of technology roorkee 2. Petrophysical characterization using the considered shaly sand analysis models will enable a better evaluation of the reservoir quality and. An integrated formation evaluation approach for maximizing the value of mature shaly sand reservoir a case study from ravva middle miocene reservoir sudipto datta, bernd herold, tim osullivan, kausik saikia and vivek shankar, cairn india limited, kumar praveer, petrofac summary. Although openhole logs were run, the operator needed greater insight into the formation and its fluid contents. Evaluation of gas hydrate saturation by effective medium.
Therefore, shaly sands are heterogeneous producer reservoir. Connectivity equation and shalysand correction for. Gas while drilling gwd classification in shalysand. Inclass and homework exercises are based on real problems actually faced, by the instructor. Text i have yet to find the ideal petrophysics or formation evaluation text book. Core data from well tut8 was from the depth 8284 ft to 8373 ft with 90 data points and core data from well tut12 was from the depth 8194 ft to 8378 ft with 179 data points. When developing oil and gas fields, there are often the reservoirs consisting of alternating thin sedimentary thin layers of various rocks, clays, siltstone and sandstone fig. The shale and silt fractions have a large influence on values of effective porosity, water saturation and permeability. This work presents a formation evaluation for two main santonian sequences of an important gas field composed of siliciclastic reservoirs in santos basin, eastern brazilian margin. Artificial neural network ann prediction of porosity and. The relationship between the resistivity index and the water saturation is also expressed in terms. Formation evaluation for thin bed shaly sand reservoirs. Summary formation evaluation from well logs in laminated shaly.
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