辽河双台子油气藏气顶驱开采特征及气窜模式

CHARACTERISTICS OF GAS-CAP DRIVE PRODUCTION AND GAS BREAKTHROUGH PATTERN OF SHUANGTAIZI OIL AND GAS RESERVOIR IN LIAOHE

辽河双台子油气藏为国内典型气顶砂岩油气藏。该油气藏为断块分隔的背斜圈闭 ,油层为扇三角洲相砂岩 ,具厚度大、粒度粗、分选好、渗透率高的特点。投入气顶驱开采 19年 ,取得较好效果。其开采特征表现为 :老井初产好产量高 ,其产量受油层厚度影响不大 ,加密井则生产较差 ,并且对老井有明显的干扰。开发中油井气窜十分普遍 ,依据该油藏的地质动态特征 ,可将气窜归纳为两种模式 :垂向气窜与侧向气窜。垂向气窜发生在穿过气顶的油井中 ,气顶气自本井上部窜入下部油层 ,由于距离近 ,故气窜发生快而严重 ;侧向气窜发生在构造翼部靠近气顶的纯油井中 ,气顶气自临近的气顶侧向窜入油层 ,由于距离较远 ,故气窜发生慢且平缓。鉴于该油气藏极低的原油粘度与较高的渗透性 ,其 6 0 0m井距已可有效控制储量 ,井网加密似嫌多余。

The Shuangtaizi oil and gas reservoir in Liaohe is a typical gas-cap sandstone reservoir in China.The reservoir is an anticlinal trap separated by fault block.The oil-bearing formation is fan-shaped delta facies sandstone,having such characteristics as great thickness,coarse grain size,good degree of sorting and high permeability,etc.In 19 years after the reservoir was put into production by gas-cap drive,a good effect has been obtained.The production characteristics are that the initial output of the wells drilled in early stage is high and the influence of the pay′s thickness on the output is not too great,while the output of the additional wells is relatively poor and obviously disturbs the output of the initial wells,and in the process of development,the gas breakthrough is very common.According to the geologic performance characteristics of the oil reservor,the gas breakthrough can be summed up into two patterns——vertical gas breakthrough and lateral one.The vertical gas breakthrough occurs in the wells which penetrates gas cap and the gas-cap gas percolates from upper formation into lower one,and the Occurrence of gas breakthrough is quick and grave due to small distance between the upper formation and lower one;the lateral gas breakthrough occurs in the oil wells on the structural flank and near to gas cap,and the gas-cap gas laterally penetrates into oil-bearing formation from adjacent gas cap and the occurrence of gas break-through is slow and smooth due to large distance.Seeing that the viscosity of the crude oil in this oil reservoir is extremely low and the permeability is relatively high,the well spacing of 600 m can effectively control the reserves,and it seems unnecessary to fill well pattern.