塔里木盆地塔中83井区气侵定量研究

Quantitative Gas Washing Evaluation on Reservoirs in TZ83 Well Block in Tarim Basin

喜山期的干气对塔里木盆地塔中Ⅰ号坡折带古油藏气侵作用是导致油气分馏形成凝析气藏的重要原因,前人关于塔中地区气侵的研究多为定性描述,而定量化的研究较少。以处于塔中Ⅰ号坡折带内带的塔中83井区为研究对象,剖析研究区的成藏地质条件,总结其油气性质、组分特征,进而开展原油样品正构烷烃定量测试,计算研究区不同油气藏的原油正构烷烃损失率Q,对其气侵强度进行了定量化评价。正构烷烃损失率Q的计算结果表明,研究区油气藏都遭受了不同程度气侵(Q变化范围为12%～86%),气侵强度在平面上表现出由北西向南东逐渐减小,剖面上由下向上逐渐变小,同时,气侵导致油气性质改变,原油中的低碳数正构烷烃溶于气相,脱离油相形成与凝析油伴生的高含腊量原油,证实了沿塔中82走滑断裂和塔中Ⅰ号断裂交汇部位充注的高—过成熟度干气对研究区油气藏的气侵作用,为该区油气成藏研究提供了定量证据。

In Himalayan period,the dry-gas washing to the ancient reservoirs in the Tazhong No.1 slope break is an important reason that leads to the oil and gas fractionation and the formation of secondary gas condensate reservoir.Most of the previous study on the gas washing in Tazhong is qualitative description,but quantitative research is less,which pulls off the further accumulation research.This paper analyzed the regional structure conditions,summed up the oil and gas properties and component characteristics,made the quantitative description of gas washing by carrying out the n-alkanes quantitative measurement and calculating the loss rate of n-alkanes（Q） in the TZ83 well block.The results of the loss rate of n-alkanes show that all reservoirs in the study area had experienced gas washing（range of Q is 12% to 86%）,and the intensity of gas washing gradually decrease from the northwest to southeast in the plane and from deap to shallow in the cross section.Furthermore,during the gas washing,the lower carbon number n-alkane dissolved in gas and separated from oil,led to the formation of condensate gas reservoirs with high wax content.It is confirmed that the gas washing of high-maturity dry gas to TZ83 well block along the interchange of Tazhong 82 and the Tazhong No.1 slope break and provides quantitative evidence for the accumulation research.