Abstract

The early development of offshore heavy oil fields mainly adopts the method of large well spacing and multilayer combined production development. After entering the high water cut period, it is faced with the problems of low oil production rate, rapid production decline and low recovery factor, and lack of experience of development adjustment in high water cut period, which result in oilfields in low level development stage for a long time. Taking Qinhuangdao 32-6 oilfield as the target area, the study of stratigraphic subdivision and well pattern adjustment in high water-cut period was studied by using laboratory physical experiments and reservoir numerical simulation, and the technical limits of stratigraphic subdivision for offshore heterogeneous heavy oil reservoirs, well pattern adjustment model and horizontal well layout technology were defined. The results show that when the permeability ratio is greater than 3 or the reservoir viscosity ratio is greater than 3, the interlayer interference coefficient is more than 0.2, and the stratified development should be carried out. For strong heterogeneous reservoirs, the basic inverse nine-spot well pattern is adjusted to a five-point horizontal well pattern by infilling horizontal production wells between injection and production wells, and the spacing of injection-production wells is reduced from 350 m to 220 m, and the volume sweep coefficient is increased by 26%. For the bottom water heavy oil reservoir with the viscosity of 260 mPa·s, the horizontal well can greatly improve the initial production and cumulative oil production of the single well by optimizing the distribution of wells with interlayers (parameter: interlayer permeability, distribution area and distribution location) within the reservoir. When the cumulative oil production of horizontal well reaches 50, 000 m3, the height of the oil column can be pushed down to 7 m. Based on the above research results, a new model for development and adjustment for horizontal wells for development adjustment of horizontal well stratification system in high water cut period has been formed. It was applied to QHD32-6 oilfield, and 124 horizontal wells have been implemented. After adjustment, the oil production rate has increased 2.5 times, the recovery rate has increased by 12.8%, and the oilfield development effect and economic benefit are greatly improved, which can provide an important reference for the development adjustment of similar oilfields in high water cut period.

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