被断裂破坏泥岩盖层封闭性演化史恢复方法及其应用

前人研究泥岩盖层封闭性时并没有考虑断裂的破坏程度，且对已被断裂破坏泥岩盖层封闭性演化史的研究目前尚未见到文献报道，而这些问题对含油气盆地断裂发育区油气勘探至关重要.在被断裂破坏泥岩盖层封闭机理及其封闭演化特征研究的基础上，通过比较泥岩盖层断接厚度与其封油气所需的最小断接厚度的相对大小，将被断裂破坏泥岩盖层封闭分为未被断裂破坏和已被断裂破坏泥岩盖层封闭2种，并通过泥岩盖层和断层岩古排替压力恢复，确定泥岩盖层封闭能力形成距今时间、断层岩开始压实成岩距今时间和封闭能力形成距今时间，建立了一套被断裂破坏泥岩盖层封闭性演化史的恢复方法，并将其应用于渤海湾盆地南堡5号构造被f₂断裂破坏东二段泥岩盖层封闭性演化史的恢复中.结果表明:在L₁、L₃、L₄、L₅、L₆、L₇和L₉测线处，f₂断裂未破坏东二段泥岩盖层封闭，仍是东二段泥岩盖层封闭，其封闭性演化经历了不封闭和封闭阶段，目前具有较强的封闭能力.在L₂和L₈测线处f₂断裂已破坏了东二段泥岩盖层封闭，为f₂断裂断层岩封闭，其封闭能力演化经历了压实不封闭、成岩不封闭和成岩封闭3个阶段，目前也已具较强封闭能力，均有利于油气在东二段泥岩盖层之下储层中聚集与保存.与目前东二段泥岩盖层之下储层中已发现油气分布相吻合，表明该方法用于恢复被断裂破坏泥岩盖层封闭性演化史是可行的. 

Restoration Method of Closed Evolution History of Fractured Mudstone Cap Rock and Its Application

The failure degree of mudstone caprock was not considered in the previous study, and the study on the evolution history of the sealing characteristics of fractured mudstone caprock has not been reported in the literature, however, these problems are very important for oil and gas exploration in fault development area of petroliferous basin. On the basis of the study of the sealing mechanism and the closed evolution characteristics of fractured mudstone cap rock, by comparing the relative size of the fault contact thickness of the mudstone cap rock and the minimum fault contact thickness required for sealing oil and gas, the fractured mudstone cap rock sealling type is divided into 2 kinds, including non-fractured and fractured mudstone cover. And the mudstone cap rock sealing formation time, fault rock compaction time and sealing capacity formation time were determined by recovering the ancient displacement pressure of mudstone cap rock and fault rock. A restoration method of the closed evolution history of fractured mudstone cap rock is established, then it was applied on the restoration of closed evolution history of the fractured mudstone cap rocks damaged by f₂ fault of Ed₂, Nanpu 5 structure, Bohai Bay basin. The results show that fault f₂ did not destroy the Ed₂ mudstone cap rock sealing ability in L₁, L₃, L₄, L₅, L₆, L₇ and L₉ test line, and is still mudstone cap rock sealling of Ed₂, its closed evolution has experienced non-closed and closed phases. At present, it has strong sealing ability. The Ed₂ mudstone cap rock sealing in L₂ and L₈ test lines was destroyed by fault f₂, its sealing ability comes from f₂ fault rock, the evolution of its sealing ability has experienced 3 stages:compaction period not closure, diagenetic period not closure and diagenetic period closure. At present, it has a strong ability of closure, which is favorable for the accumulation and preservation of oil and gas in the reservoir under the mudstone caprock of Ed₂. The prediction results are consistent with the discovered oil and gas distribution in the reservoir under the Ed₂ mudstone cap rock, which shows this method is feasible to restore the closed evolution history of mudstone cap rock.