Inflow Control Device in Thin-Layer Bottom Water Drive Reservoir Enhances Oil Recovery in China South Sea

Abstract

Horizontal wells can increase a reservoir's drainage area and hydrocarbon recovery, but they pose challenges such as early water breakthrough, high water cut and low oil recovery. Water production continues to increase until the economic limit of the well is reached. In a thin-layer water drive reservoir, in particular, the key factors are controlling water coning, extending the water-free production period and controlling water production post breakthrough.This paper details the challenges faced working in horizontal wells, an optimized reservoir Passive Inflow Control Devices (PICDs, called ICD in this paper) mechanism to address such challenges and reservoir simulation analysis in the application of ICDs in China South Sea.Two dynamic reservoir models were built with the same reservoir property inputs but with two well completion types: standalone screen (SAS) completion and ICDs completion. Through the daily oil and water production, cumulative oil and water production, 3D water movement, the performance of an ICD completion were evaluated. The simulation results demonstrate the added value of the ICD completion system compared to a standalone screen completion production and increased oil in a thin-layer bottom water driver reservoir. IntroductionIn a well producing from a bottom water drive reservoir, oil production is promoted by water production. As a primary reservoir drive mechanism, water moves into the pores spaces originally occupied by oil, displacing it to the producing well. Oil withdrawn from the reservoir is replaced volume for volume by encroaching water. In such a scenario, the reservoir pressure remains stable or gradually declines during production. In addition to providing drive energy and displacing oil, an active aquifer poses severe coning issue, typically for vertical wells.A horizontal well is generally more productive than a vertical well and drilling horizontal wells has become an established method of improving recovery of oil and gas. More contact yields a larger reservoir drainage area and less drawdown required to produce the same amount of fluid. Reducing drawdown is a typical technique for a thin-layered water drive reservoir and maximum production rates are limited as a result of coning problems. Although, factors such as heel-to-toe effect, formation heterogeneity, unfavorable oil/water mobility ratio, high reservoir pressure contrast and fractures accelerate early water production, they result in unbalanced oil contributions from the well and low oil recovery.The reservoir formation mentioned in this paper is sandstone with an anticline structure, and immature faults overriding a large aquifer. The production layer is approximately 30ft, which poses difficulties for controlling water breakthrough and high water cut. Furthermore, this thin pay zone is highly heterogeneous and unforable mobility ratio under the reservoir condition. All factors pose challenges for oil recovery.Data from offset wells in this block experienced early water breakthrough and rapid growth of water cu...