Discovery and Effective Development of Attic Oil in the Edge and Bottom Water Reservoirs with Gas Caps at High Watercut Stage–An Example from South Block of Layer M-II of Aryskum Oil and Gas Field

The southern area of the Cretaceous M-II layer in the Aryskum oil and gas field has entered the high watercut stage after a development of 10 years due to the invasion of edge and bottom water, there is a severe water flooding inside the reservoir and infill wells cannot be implemented. In order to improve the reservoir development effect, it is necessary to study the potential of reservoir scrolling development. In view of the complex characteristics of gas cap and faults in reservoirs, firstly, seismic interpretation techniques are applied to finely characterize secondary faults and accurately identify micro-structures. Then the numerical simulation technology is applied to determine the remaining oil distribution and oil-water movement driven by edge-bottom water. Through the structure-oriented filtering process, using the fault classification recognition technology of coherent curvature multi-body fusion, 10 secondary small faults are newly depicted, which provides a basis for understanding remaining oil. The high-precision fine numerical simulation results show that the aquifer volume in the southern area is 78.6 times of the oil ring. During the development process, with the decrease of the oil ring pressure, the strong edge and bottom water invasion causes the oil ring to be flooded, and at the same time, the crude oil in the oil ring flows to the gas cap area, encountering the shelter of the newly interpreted fault, forming the attic oil storage. The innovation of this paper is that the attic oil is newly discovered, which is a favorable area for the scrolling development of the reservoir to tap the potential. From 2011 to December 2021, 50 new wells were drilled in the attic oil potential area. The average daily oil production of single new well is 41.5t/d, and the cumulative oil production is 131.28 × 104t.