基于砂箱物理模拟的断层封闭有效性评价新方法

New methods for evaluation fault sealing effectiveness based on sand box physical simulation

泥岩涂抹的连续性影响油气跨断层运移,在相似岩性、相似应力条件下,泥岩厚度和断距长度是影响泥岩涂抹连续性的主要因素。本文结合岩芯观察,借助三维定量物理模拟实验对泥岩涂抹的连续有效性进行了研究。结果表明:①泥岩有效涂抹是决定断层封闭性的必要条件,涂抹连续厚度是封闭性评价的重要参数;②受剪切作用在断层带中形成连续的泥岩涂抹油气封堵层,其涂抹形成过程分为3个阶段即泥岩层未错断阶段、泥岩剪切涂抹层形成阶段和涂抹层连续性破坏阶段,其中前2个阶段是泥岩有效涂抹阶段,在第3个阶段出现泥岩涂抹连续性破坏从而导致封堵油气失效;③基于非连续性等比例模型提出了新的断层封闭性评价参数——泥岩连续涂抹最小厚度,建立了泥岩失去涂抹连续性的非等比例评价理论和数学模型,形成了基于断裂带泥岩连续涂抹断层封闭性评价参数SGR_(new)新算法。结果表明,考虑了泥岩涂抹有效性而识别的断块圈闭可靠程度高,目标优选更准确,在研究区块圈闭评价应用效果好。

Objectives:The continuity of shale smear influences hydrocarbon migration across faults.In similar condition of lithology and stress,the shale thickness and fault distance are the main influencing factors of shale smear continuity.Methods:In this paper,by using core data,the distribution characteristics of shale smear in faults are observed and analyzed,and the effectiveness of shale smear is studied by means of 3D quantitative physical simulation experiment.Results:The following researching results are obtained.First,effective shale smear is the necessary condition of fault sealing,and the continuous thickness of shale smear is an important parameter of sealing evaluation.Second,the shale smear forming process in shear fault zone is proposed,which can be divided into three stages,i.e.the shale layer is not completely faulted,the shear shale smear is formed and the continuity of shale smear is destroyed,among the effective shale smear is the former two stages.Third,based on the non-continuous equal proportion model,a new fault sealing evaluation parameter is presented,and the non-equal proportion evaluation theory and mathematical model are established,and a new sealing system evaluation calculation method is further formed.Conclusions:The results show the non-equal proportion evaluation method considered the shale smear effectiveness coefficient can be applied to determine the effective fault block trap and improve the success rate of exploration,and yield good exploration efficiency in study area.