Distribution and Continuity of Sandstone Reservoirs

Abstract

Includes Parts 1 and 2 This paper presents brief discussions of the three most importantdepositional environments of sandstone reservoirs. Criteria for identifyingsandstones from conventional data are presented, along with conceptual modelsfor predicting their distribution and internal reservoir characteristics. Introduction Effective maximum exploitation of a hydrocarbon accumulation requires fullunderstanding of the reservoir beds and the pore space they contain.Fundamental research on clastic sediments by the petroleum industry, universities, and government agencies has produced a wealth of publishedinformation on the distribution and continuity of sandstones. Criteria forrecognizing the various types of sandstones utilizing conventional subsurfacedata, such as cores, cuttings, and well logs, are reasonably well established.Conceptual models for predicting or determining sand body distribution, predicting or determining sand body distribution, continuity, and internalcharacteristics also are available. Any method of oil- or gas-field developmentthat does not take advantage of these conceptual models and criteria must beconsidered negligent. The distribution, continuity, and internal characteristics of sandstones arecontrolled primarily by original environments of deposition. Anyone who isseriously involved in determining the distribution and continuity ofsandstones, whether on a local or regional basis, will profit substantially bystudying the literature and developing a thorough understanding of theseenvironments. Therefore, this summary paper on the distribution and continuity ofsandstone reservoirs consists of two parts. Part 1 consists of briefdiscussions of the three most Part 1 consists of brief discussions of the threemost significant sandstone depositional environments:continental (alluvialfan, braided stream, meandering stream, and aeolian),transitional (deltaicand coastal barrier islands, tidal channels, and aeolian and transgressivemarine), anddeep marine (turbidities related to submarine canyon-fansystems). (See Fig. 1.) These key sedimentary environments are reviewed through examination of modemexamples and ancient analogs. Criteria for identifying sandstones fromconventional data are presented with the conceptual models necessary forpredicting their distribution and internal reservoir characteristics. Part 2 is a bibliographic source document. It includes a geneticclassification of environments of sand deposition and lists, by depositionalenvironments and geographic occurrence, the significant literature on ancientsandstones. Some 250 selected references are included. The scientist and engineer who together integrate appropriately thecriteria, principles, and models of sandstone deposition presented here withother subsurface engineering data should benefit from the synergism bound tooccur and, thus, should be better able to solve the practical reservoirproblems. Distribution and Continuity of Sandstone Reservoirs Our present knowledge and understanding of the factors that control thedistribution and continuity of sandstones are based on the research on Recentsediments and on the study of ancient clastic sediments. The following discussion of the distribution and continuity of sandstonereservoirs describes those sand bodies believed to predominate in the spectrumof sandstone reservoirs. JPT P. 776