Single-layer outer edge waterflooding development model of complex fault block reservoirs with high water cut

Abstract

In the late stage of development， the complex fault block reservoir faces a series of problems， such as high comprehensive water cut， lack of formation energy， complex remaining oil distribution， and poor well pattern suitability. In this paper， based on the oil-water distribution status of the waterflooding reservoir， such as water-in-oil and oil-in-water， the development mode of single-layer outer edge waterflooding was studied through theoretical model derivation and numerical simulation methods by taking Ken71 fault block reservoir in the middle of Zhanhua Sag of Jiyang Depression as an example. The results show that the reasonable water injection volume， fluid production volume， and spacing between injection and production wells during single-layer development can be obtained through the force analysis of the fluid production end and the water injection end. The key factors affecting the remaining oil saturation and the water saturation are reasonable water injection pressure difference， water injection volume， and fluid production volume of single-layer development systems. It is essential in controlling the reasonable formation pressure level and the secondary enrichment of the remaining oil. The spacing between injection and production wells increases to the periphery of the oil-water boundary， and 2.9 times the width of the oil-bearing strip is the critical value of reasonable spacing between injection and production wells. An asymmetric periodic injection and production method with short injection and long standing is adopted to establish a single-layer outer edge waterflooding development model， which is beneficial to maintain the stability of the pressure system and increase the sweep efficiency of the remaining oil of the single-layer， so as to improve the oil recovery. Field application shows that after applying the single-layer outer edge waterflooding development model， the daily production of Ken71 fault block increases to 254 t， the water cut is controlled to 93.7%， the recovery increases to 31.53%， and the oil recovery rate is increased by 4.9%， which shows an excellent yield-increasing effect. The single-layer outer edge waterflooding model solves the problems in the development of complex fault block reservoirs with high water cut， such as dispersed remaining oil distribution， low waterflooding sweep efficiency， and poor well pattern suitability and can provide guidance and reference for complex fault block reservoir development.

Keywords

• single-layer outer edge waterflooding
• development model
• periodic waterflooding
• numerical simulation
• complex fault block reservoir