苏里格气田苏A区块未动用区过剩压力预测

Prediction of excess pressure in undeveloped area of Su A block in Sulige Gas Field

苏A区块未动用区占区块面积44%,如何有效开发未动用区成为区块持续稳产的关键,近年来常规方法没有取得突破。研究认为,欠压实泥岩盖层中过剩压力对气体运移富集的导向作用可实现未动用区潜力目标优选。由于苏里格气田石盒子组顶部区域泥岩盖层普遍存在欠压实,单井表现为泥岩声波时差偏大,偏离正常压实曲线,在欠压实泥岩内流体存在过剩压力,井控区可以通过等效深度法计算过剩压力,而未动用区过剩压力空缺。研究发现苏A区块过剩压力最大值先出现在石盒子组盒1+2段,声波时差形成突变,与下部盒3段地层产生波阻抗差界面,在地震剖面上表现出强振幅反射;过剩压力与地震反射均方根振幅有相关性,在均方根振幅平面约束下,基于完钻井过剩压力数据,实现了未动用区过剩压力预测,确认过剩压力小有利于气体富集,未动用区4个过剩压力低值区成为有利潜力目标。实施部署的评价井取得很好效果,明确了该区块下步产能接替方向。

The undeveloped area of Su A block accounts for 44%of the block area.How to effectively develop the undeveloped area has become the key to the sustainable and stable production of the block,conventional methods have made no breakthroughs in recent years.The study indicates that the guiding effect of excess pressure on gas migration and enrichment in undercompacted mudstone caprock may optimize the undeveloped area potential targets.Due to the widespread undercompaction of mudstone caprock in the top area of Shihezi Formation of Sulige Gas Field,the single well shows that the mudstone interval transit time is large and deviates from the normal compaction curve.There is excess pressure in the fluid in the undercompacted mudstone.The excess pressure in the well control area can be calculated by the equivalent depth method,while the excess pressure in the undeveloped area is vacant.It was found that the maximum excess pressure in Su A block first appears in He 1+2nd Member of Shihezi Formation,interval transit time forms abrupt changes,resulting in wave impedance difference interface with the lower He 3 Member formation,and showing strong amplitude reflection on the seismic profile.The excess pressure is correlated with the RMS amplitude of seismic reflection.Under the constraint of the RMS amplitude plane,the prediction of excess pressure in the undeveloped area is realized based on the drilled well excess pressure data.It is confirmed that low excess pressure is conducive to gas enrichment,and four low excess pressure areas in the undeveloped area have become favorable potential targets.The appraisal wells deployed and implemented in the block have achieved good results,and the next production capacity replacement direction has been made clear.