186 / 2022-02-28 16:02:14

Reservoir lithofacies architecture patterns and its controlling effect on sweet spots of terrestrial mixed fine-grained rocks

mixed fine-grained rock; lithofacies architecture; shale oil; UAV; mixed shallow lacustrine deposits zone; sweet-spot; Lucaogou Formation; Jimsar Sag

In the process of shale oil development, lacustrine mixed fine-grained rocks lithofacies controlling effect of the sweet-spot can be quite complex. Based on the core, outcrop, logging, testing and production data, the classification, 3D prototype model and combination pattern are carried out through lithofacies architecture analysis, UAV and 3D geological modeling technology. The research shows that: (1) Combining traditional fieldwork with UAV photography to characterize the 3D spatial distribution characteristics of the lithofacies architecture of the outcrop section of the Lucaogou Formation. The stratigraphic-structural models and three-dimensional lithofacies prototype models are presented from well setting and lithofacies types quantitatively characterizing. It is believed that its lithofacies architecture has relatively stable but vary locally. (2) The lithofacies architecture combinations of mixed fine-grained rocks are mainly divided into three types: gradient type, mutation type and special type. The graded types characterized by symmetrical lithofacies architecture and a superposition of multiple similar cycles, are widely developed. The reservoir in the graded types is a high-quality reservoir with developed dissolution pores, and is a mixed beach-bar microfacies in a mixed rock belt. The mutant type can be subdivided into two types. The development degree of the sand body is average, characterized by asymmetric lithofacies architecture and a superposition of multiple similar cycles. And the reservoir is a thin reservoir with high-quality hydrocarbon generation. The special type belongs to the thick clastic rock with a high degree of sand body development. It is a relatively reservoir with tight reservoir properties and superimposed by a single cycle of sand bodies. (3) The lithofacies architecture controls the distribution of sweet spots and development strategies. The graded type reservoir shows weak heterogeneity and well-developed sand. This type of reservoir has the best development effect and is suitable for large-scale deployment of horizontal well platform operations. Mutant type reservoirs are well developed, but it shows strong heterogeneity and average development effect. And they are the follow-up succession area. The special type reservoir is distributed with poor continuity, strong heterogeneity, and good development effect. The deployment of horizontal wells requires meticulous research on the lithofacies architecture and NMR oil bearing saturation.