In any petroleum province in the world where there are sandshale sequences, the geologist, engineer or log analyst confronts toe shaly sand problem. When heavier minerals are also present in the formation in variable amounts. Consequently, the methods and techniques in the shaly sand models can be used to improve petrophysical evaluation of shaly sand reservoirs. The shale volume is about 9 percent and formation water resistivity for virgin zone is 0. The water saturation distribution above the fwl in a reservoir is controlled by the balance of. Examples with an exercise part sandstone reservoir, shaly sand interpretation, complex mineralogy.
Connectivity equation and shalysand correction for. A modified approach for volumetric evaluation of shaly sand. Pdf improved reservoir description of shaly sands using. Tongue of the castlegate sandstone, and mancos shale, eastern book cliffs, colorado and utah, usgs. Hydrocarbon are stored only in pore space in sand matrix. Shaly sand petrophysics inhouse training by petroskills. Advanced methods for interpreting well logs, shaly sand analysis, and production logging methods. Each of these can furnish a significantly different reservoir evaluation. Quantitative log interpretation and uncertainty propagation of petrophysical properties and facies classification from rockphysics modeling and formation evaluation analysis using kernel principal component analysis to interpret seismic signatures of thin shaly sand reservoirs.
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. Responses of the three porosity logs in more complex. 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. A valuable reference dedicated solely to well logging and formation. Hydrocarbon saturation assessment of thick shaly sand reservoir. Shaly sand formation evaluation using a single membrane. The conventional resistivity in a laminated shaly sand formation for the sand resistivity rsd of. The model showed that the conductivity of water saturated shaly sand co was directly related to the shaliness factor qv, conductivity of formation water cw, and porosity. Review of existing shalysand models and introduction of a. Examples with an exercise part sandstone reservoir, shaly sand interpretation, complex mineralogy of a carbonate reservoir help to understand the different methods and algorithms.
Formation water resistivity r w regime for simandoux and indonesian models 2. The conventional resistivity in a laminated shaly sand formation for the sand resistivity r sd of 20. Petrophysical evaluation of shaly sand reservoirs in palouge. In thin lamination shalysand, fine grained of sand, silt and clay were. Scribd is the worlds largest social reading and publishing site.
Packed with moneysaving and time saving strategies for the engineer working in the field. Toby darling, in well logging and formation evaluation, 2005. Shaly material can be distributed in the formation in three ways. Formation evaluation in thin sandshale laminations. An integrated formation evaluation approach for maximizing. This course can be conducted on site at your location exclusively for your staff. The result of the evaluation was utilized to investigate the low productivity from some zones and its relation with depositional process and petrophysical properties. Basic well logging and formation evaluation bookboon. Shaly sand interpretation qed pete 321, sections 501506 spring. Comparing the results of different shalysand evaluation methods is dif. Shale is composed of silt, clay and their bounded water which will not flow. Page 311 electrical conductivities in shaly sands i. A practical guide aapg continuing education course note asquitt, george b.
Pdf reservoir evaluation of shaly formations has long been a difficult task. 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. Advanced petrophysics training in evaluation sandstone formations. The evolution of shalysand concepts in reservoir evaluation. Petrophysical models and techniques for shalysand formation. Sharma center for petroleum and geosystems engineering, the university of texas at austin, cpe 2. Determination of shale volume and distribution patterns and. Sandor, shell international exploration and production b. Openhole log analysis and formation analysis book osti. Laminated shaly sand analysis and 3d saturation height modelling. The course covers solutions for evalating various shaly sand reservoirs including. This course tackles the important and nontrivial problem of practical formation evaluation in shaly sand provinces. It may also depend on the way the shale is distributed in the formation. Basic formation evaluation university of southern california.
Landmark papers in well logging and formation evaluation. In the application of these models to specific formations, industry follows no axiomatic approach in terms of critical factors such as 1. Integrated petrophysical evaluation applied to the. As a result, a shaly sand with gas can look on the log as though the tool is in a liquid filled clean sand. On the application of simandoux and indonesian shaly sand resistivity interpretation models in low and high rw regimes k. A valuable reference dedicated solely to well logging and formation evaluation. Well logging and formation evaluation sciencedirect. Openhole log analysis and formation evaluation, 2012 edition, by richard m. Advanced formation evaluation in sandstones next training. This in turn makes seeking enhanced reservoir description of shaly sand. Conventional wireline logs often fail to provide a reliable evaluation of reservoir quality and producibility in shaly mud formations, particularly in the shaly gas sand reservoirs of the rocky mountains which are characterized by low porosity i. I have yet to find the ideal petrophysics or formation evaluation text book. The relationship between the resistivity index and the water saturation is also expressed in terms of a single membrane potential measurement.
The course covers solutions for evalating various shaly sand reservoirs including technqiues and equations. Gas normally has little effect on the acoustic log, unless the formation is uncompacted. 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. R ar o w m 1 where r o is the formation resistivity of watersaturated sediment, r w. A practical guide aapg continuing education course note by asquitt, george b. 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.
This paper has been cited many times through the years, and books and training. In many fields with good quality carbonate reservoirs, evaluation is simpler than with sandstone because the shaly sand problem does not occur and beds tend to be thicker. Shale is the most common, and certainly the most troublesome, rock type that must be drilled in order to reach oil and gas deposits. The laminated shaly sand analysis lssa technique is a log analysis model specifically designed for the evaluation of thinbedded, lowresistivity sandshale sequences using vertical. This course will be suitable for all geoscientists and engineers who will benefit greatly from exposure to advanced knowledge and expertise in formation evaluations in clastics. Of course, the hydrocarbon inplace is obtainable once porosity and water contents are estimated in the formation. This leads to large uncertainties in the apparent sand resistivity even for. Shaly sand petrophysics training course petroskills aps. A new equation is derived that directly relates shaly sand conductivity to the membrane potential. 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. In such a situation, archies model works very well.
The sand percentage here is generally less than 30%. Water saturation equations in shaly reservoir rocks ptrl3023. Siyamak moradi 1, mohammad moeini 1, mohammad kamal ghassem alaskari 2 and elaheh hamed mahvelati 1. Shaly synonyms, shaly pronunciation, shaly translation, english dictionary definition of shaly. Well logging and formation evaluation oil and gas news. Choice of respective shale function v sh from gamma. Summary formation evaluation from well logs in laminated shaly sands has often suffered from lack of proper. The way shaliness affects a log reading depends on the amount of shale and its physical properties. The formation evaluation problem is a matter of answering two questions. 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. Subject are the fundamental techniques of well loggingborehole geophysics and the interpretation of measured data formation evaluation. In lo g interpretation of shaly sand is used matrix densit y of quartz d. In shaly sand zones having a high proportion of conductive dispersed shales. This leads to large uncertainties in the apparent sand resistivity even for relatively small volumes of laminar shale because the conventional resistivity measurements are made horizontally into the formation.
On the application of simandoux and indonesian shaly sand. Inverse of the electrical formation factor versus the porosity in. 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. Shale can exist in the form of laminae between which are layers of sand. Development and field applications of shaly sand petrophysical models a dissertation submitted to the graduate faculty of the louisiana state university and agricultural and mechanical college in partial fulfillment of the requirements for the degree of doctor of philosophy in the department of petroleum engineering by milton n. Determination of shale volume and distribution patterns and effective porosity from well log data based on crossplot approach for a shaly carbonate gas reservoir. Comprehensive coverage of the latest technologies and practices, including, troubleshooting for stuck pipe, operational decisions, and logging contracts. Electrical properties, petrophysics and formation evaluation. Yet, no one method predominates within the industry. What are the lower limits for porosity, permeability and upper limits for water saturation that permit profitable production from a particular formation or pay zone.
The following definition and petrophysics model are a typical shaly sand formation model which assumes. T total porosity phit, which includes the pore space in sand and shale. Dualwater method of shaly sandstone evaluation dual water model. Subsurface and petrophysical studies of shalysand reservoir. Containing shale, a finegrained, impermeable, sedimentary rock composed of clays and other minerals, usually with a high percentage of quartz.
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