Integrated Interpretation of 3D Seismic and Wireline Data to Delineate Thin Oil-Producing Sands in San Jorge Basin, Argentina (2000)

Integrated Interpretation of 3D Seismic and Wireline Data to Delineate Thin Oil-Producing Sands in San Jorge Basin, Argentina Carlos Torres-Verdin; Carlos Torres-Verdin The University of Texas at Austin Search for other works by this author on: This Site Google Scholar Raghu K. Chunduru; Raghu K. Chunduru Baker Atlas Search for other works by this author on: This Site Google Scholar Alberto G. Mezzatesta Alberto G. Mezzatesta Baker Atlas Search for other works by this author on: This Site Google Scholar Paper presented at the SPE Annual Technical Conference and Exhibition, Dallas, Texas, October 2000. Paper Number: SPE-62910-MS https://doi.org/10.2118/62910-MS Published: October 01 2000 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Torres-Verdin, Carlos, Chunduru, Raghu K., and Alberto G. Mezzatesta. "Integrated Interpretation of 3D Seismic and Wireline Data to Delineate Thin Oil-Producing Sands in San Jorge Basin, Argentina." Paper presented at the SPE Annual Technical Conference and Exhibition, Dallas, Texas, October 2000. doi: https://doi.org/10.2118/62910-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search nav search search input Search input auto suggest search filter All ContentAll ProceedingsSociety of Petroleum Engineers (SPE)SPE Annual Technical Conference and Exhibition Search Advanced Search AbstractHydrocarbon-bearing sand units in San Jorge Basin, Argentina exhibit thicknesses between 0.5 and 15m, with a mean value of 1.5m. These sand units are associated with ephemereal and laterally heterogeneous fluvial architectures embedded within much thicker shale units of lacustrine and flood-plain origin. Tuffaceous laminations originated from pulses of volcanic activity are also present in the sedimentary column. In view of the wide range of spatial variability and size of porous sands, a typical well is planned to intersect vertically as many sand units as possible. The best producing sands have average porosities of 10% and permeabilities of a few millidarcies. There are several problems faced by the petrophysicist in assessing whether or not a given sand unit should be perforated, namely,discrimination between oil- and water-bearing sands is not trivial because of very low salinity water,there exist substantial vertical variations of effective porosity within an individual sand because of shale laminations, andit is often impossible to assess lateral extent away from the well.We have successfully addressed most of these difficulties using an interpretation procedure centered about the full 2D inversion of wireline array induction data. Full 2D inversion of array induction data is necessary to accurately estimate shallow and deep resistivities, as well as invasion radii in light of significant shoulder bed effects. This procedure has been complemented with the use of borehole NMR data to provide estimates of effective porosity within individual sand units. Finally, we have made use of geostatistical inversion of 3D post-stack seismic data to estimate the lateral extent of hydrocarbon-bearing sands laterally away from the well. We present several application examples that yield results consistent with borehole testing and production data.IntroductionLocated in the heart of Patagonia, and extending from the Atlantic Ocean to the Andean foothills, San Jorge Basin accounts for 32% of the hydrocarbon production in Argentina (see Figure 1). The origin and subsequent geological evolution of the basin is due to the same rift process responsible for the opening of the Atlantic Ocean in early Jurassic times. Accumulation of predominantly non-marine terrigeneous sediments continued until well into early Cretaceous times (Fitzgerald et al., 1990). Clastic deposition in the hydrocarbon producing zone is characterized by thick shale laminations of lacustrine and flood-plain origin, interspersed with much thinner and laterally sparse sand units which nowadays serve as hydrocarbon reservoirs. The relatively small concentration of sand units in the sedimentary column is explained by their ephemereal fluvial origin, which could only account for effective clastic accumulations between 0.5 and 15m, but predominantly thinner than 4m. Starting in early Cretaceous times, Andean tectonism caused yet another significant perturbation of the sedimentary column in the form of finely laminated deposits of pyroclastic origin (tuffs) associated with intermittent pulses of volcanic activity. These pyroclasts ranged anywhere from thin ash beds to welded tuffs several meters thick. The presence o tuffs significantly altered the original petrophysical properties of existing sand units. Subsequent structural deformation also adversely modified the already marginal porosity and permeability of the sands, and caused extensive fracture damage to the existing tuff units.In this paper, we focus our attention to oil producing sand units within the Bajo Barreal formation (mid and upper Cretaceous age) buried at depths between 1,200 and 2,900m. Figure 2 is an outcrop of the Bajo Barreal formation showing a representative sand/shale/tuff sequence with bed thicknesses similar to those encountered in the hydrocarbon-producing zone. A close-up of view of an individual sand unit is shown in Figure 2. As emphasized by that figure, the sand exhibits a fluvial cross-bedding structure and is bounded by clastic debris and tuff units above and below. Keywords: procedure, resistivity, seismic data, artificial intelligence, array-induction data, bajo barreal formation, porosity, argentina, quantitative indication, array induction data Subjects: Formation Evaluation & Management, Open hole/cased hole log analysis This content is only available via PDF. 2000. Society of Petroleum Engineers You can access this article if you purchase or spend a download.