克拉苏构造带盐下超深层断背斜裂缝带发育模式及预测方法

克拉苏构造带盐下超深层埋深大于6500 m的断背斜圈闭,白垩系砂岩储层内部裂缝普遍发育且分布复杂,对储层产能影响较大,目前仍然缺乏有效的裂缝发育模式指导裂缝带建模。本文通过钻、测井资料及物理模拟实验,分析了盐下断背斜内裂缝类型及空间分布规律:(1)盐下深层断背斜裂缝带可以分为"挤压剪切型、拱张型与调节型"三种成因类型,挤压剪切型裂缝带主要分布于断背斜翼部,受推覆作用而成,平面呈近EW走向或NW-SE走向。拱张型则主要发育于背斜核部,受控于断背斜拱张作用,平面近EW走向,调节型裂缝带则发育于断背斜的构造转换部位,呈近SN走向;(2)物理模拟实验证明拱张型裂缝带受褶皱褶曲度控制,剪切型、调节型裂缝带则受逆冲断层断距控制,根据断背斜拱升角及垂直断距变化可以预测裂缝带的平面分布;(3)地质资料和物理模拟实验证明"调节裂缝带"及"拱张裂缝带"张开程度最大,有利于改善超深层储层的储集性能,这类裂缝带的单井天然气产量较高。

Patterns of Fracture Zone in the Deep Subsalt Layer of Kelasu Structural Belt and Prospecting Method

The fractures,which have significant impacts on the well production,are well-developed in the Cretaceous low-porosity and low-permeability sandstone reservoirs in the subsalt layer of the Kelasu Structural Belt.Based on the analysis of well data and fracture physical experiment,the spatial distribution of fractures was discussed and prospecting method was proposed.(1) The fracture zones can be divided into three types.The E-W striking tension fracture zones formed in the core of the faulted anticline.E-W and NW-SE striking compressed shear fracture zones located in the wing of fault anticline.Accommodation fracture zones are distributing in the accommodation zones with striking direction of S-N paralleling the compression direction.(2) Based on the simulation experiment of clay model,we found that the tension fracture zones are controlled by fold dips,while the accommodation fracture zones are controlled by the thrust faults.So it is possible to predict the plane distribution of the fracture zone according to the dips of the faulted fold and vertical offset changes of the fault.(3) The result of the simulation experiment shows that the tension and accommodation fracture zones have large size and width,which may improve the reservoir performance.Single well test shows that these two types of fracture zone are commonly characterized by high gas production.