塔河油田缝洞型油藏氮气驱见效特征及其影响因素

Responding characteristics and influencing factors of nitrogen drive in fracture-vug reservoirs of Tahe oilfield

塔河油田氮气驱矿场试验存在气驱井组见效差异大、影响因素不明、气驱井组选择依据缺乏等问题。根据地质成因及储集体分类,将氮气驱井组划分为8种类型,选取增油特征、控水效果、能量、见效响应特征、注采井对应关系等指标,对比分析了不同类型井组注气后见效特征;其中断溶体气驱井组见效最快,控水效果最好,但稳产期较短;风化壳和暗河气驱井组见效慢,但见效后稳产期较长。研究了岩溶背景、控制构造高点、储集体发育位置、注采位置、注气速度等因素对氮气驱效果的影响。在此基础上,提出了气驱井组选井原则及实施建议为:优选水驱失效的断溶体背景的井组实施氮气驱,油价升高后,逐步扩大到风化壳、暗河背景的井组;优选控制高部位储集体的井组;优选上注下采模式的井组,优化合理注气速度。按照所提原则和建议,选取了典型井组进行注气,受效井日增油15.9 t,含水率下降35.1个百分点,取得了较好的效果。

There are many problems during the field test of nitrogen drive in Tahe oilfield,such as the difference in effectiveness of gas drive well groups,the unknown influencing factors and the lack of basis for the selection of gas drive well groups.Through geological genetic analysis and reservoirs classification,Nitrogen drive well groups are divided into eight types.The responding characteristics of different types of well groups after gas injection are compared and analyzed from five indicators,such as oil increment characteristics,water control effect,energy,responding characteristics,and the corresponding relationship between injection and production wells.Among them,karstic-fault gas drive well groups can achieve a fastest effectiveness,a best water control effect,and a relative shorter stable production period.The weathering crust and underground river gas drive well groups have a slow effectiveness,but the stable production period is longer after the effect.The influences of five factors,such as karst background,controlling structural high point,reservoir development position,injection production position and gas injection rate on Nitrogen drive effect are studied.On this basis,the well selection principles and implementation suggestions of gas drive well group are put forward as follows:the failed waterflooding well group with karstic-fault background shall be optimally selected for nitrogen drive;after the oil price rises,nitrogen drive can be gradually extended to the well group with weathered crust and underground river background;the well group with high reservoir position shall be optimally selected;the well group with upper injection and lower production mode shall be selected,and the reasonable gas injection rate shall be optimized.According to the proposed principles and suggestions,typical well groups are selected for gas injection.The daily oil production of the affected wells is 15.9 t,the water cut is reduced about 35.1 percent,and a sound effect is achieved.