【作者】 魏春光；

【导师】 万天丰； 贾庆军；

【作者基本信息】 中国地质大学（北京） ， 构造地质学， 2006， 博士

【摘要】 为了解决中海油湛江分公司涠西南油田群钻井情况复杂及钻井事故多发的难题,采用弹-塑性增量法对涠西南地区现今构造应力进行了数值模拟,在明确该地区现今构造应力场空间分布状态的情况下,研究断裂或裂隙带在现今构造应力场作用下的活动性及其活动对井壁稳定性的影响,进而预测井壁稳定性区带,提出关于钻井工程的建议意见。 涠西南凹陷油气田的构造裂缝主要形成于古近纪。通过区域构造演化研究、正断层位移-长度法对控陷断层发育过程研究、裂缝形成机制和发育阶段的研究等,将涠西南地区白垩纪以来的构造发育及应力场演化划分为四个期次:早白垩世中期—古新世(135-52Ma,最大主压应力方向为NE-SW向),始新世—渐新世(52-23.5Ma,最大主压应力方向为WNW-ESE向),新近纪—早更新世(23.5-0.78Ma,最大主压应力方向为近SN向),新构造期(0.78Ma-,最大主压应力方向为NW向)。通过对控陷断层发育和凹陷沉降中心迁移过程的研究发现,涠西南地区在古新世以前主要为NE向的涠西南凹陷的边界断层发生正断层活动,NW-SE向张裂;始新世-渐新世NE向断层以右行走滑为主,同时派生出一系列ENE向和近东西向羽状正断层(1号、2号、3号、4号断层),从而形成了一个右行走滑断层系统,该断裂系统一直控制了该区的断层和裂隙带的发育。在新近纪到现今构造应力场的作用下,该断裂系统总体上呈压剪性,相对闭合。 涠西南地区地层的主要特点是断层多,微裂缝发育,水敏性极强,存在强各向异性,尤其是涠洲组二段和流沙港流二段泥页岩地层。论文重点研究了该地区地层的非均质性,通过单井沉积微相,两个平面(涠二段和流二段)以及11条剖面的精细沉积相划分,将研究区划分出13种变形强度不同的介质,大大提高了数值模拟模型的准确性。通过调研和创新,建立了三维的、考虑井斜的测井计算地应力模型。计算了17口井,18418.05米井段的地应力数值,以及表征岩石强度大小的参数(杨氏模量和泊松比)。结合震源机制和井径测井数据等资料,确定涠西南地区现今构造应力场的最大主压应力产状为320°∠5°。 利用尽可能符合地质实际的模型参数,模拟了涠西南地区11-1N、11-4N和12-1工区两个目的层平面(涠二段和流二段)和11条剖面的现今构造应力空间分布特征,模拟结果和计算统计的数据吻合得较好,同时得到了井史资料验证的支持。明确了研究区现今构造应力场的空间分布特征,划分了井壁稳定性区带,对涠西南油田群进行了比较详细的井壁稳定性预测,提出了相应的工程措施建议。更多还原

【Abstract】 In order to solve the problem of complex and accident prone drilling condition in Weixinan oil fields of Zanjiang Division, CNOOC, the author modeled current tectonic stress field in Weixinan area by elastic-plastic incremental limited unit modeling method. The fracturing or fissure belts, controlled by recent tectonic stress field, and their influences to stability of borehole wall were studied, after 3D distribution of current tectonic stress was determined. Then, the borehole wall stability belts were forecasted and some drilling advices were provided.Most of the fractures formed in Paleogene in Weixinan depression. The tectonic evolution since Cretaceous was divided into four tectonic epochs, according to regional tectonic evolution research, study in development of dominating depression faults with displacement-length method, and in mechanism and evolution stages for fractures. They are as follows: middle epoch of Early Cretaceous - Paleocene (135-52 Ma, maximum principal compression stress orientation was NE-SW trending), Eocene - Oligocene (52-23.5 Ma, maximum principal compression stress orientation was WNW-ESE trending), Neogene - Early Pleistocene (23.5-0.78 Ma, maximum principal compression stress orientation was nearly S-N trending), and Neotectonic period (Middle Pleistocene - Holocene, 0.78 Ma-, maximum principal compression stress orientation was NW trending). By study in growth of dominating depression faults and moving of subsidence center of depression, it was found that the boundary fault of Weixinan depression was oriented in NE trending and as normal faulting extended in NW-SE orientation before Paleocene, and then which moved mainly as strike-slip fault in Eocene and Oligocene. No. 1, No. 2, No.3 and No.4 faults, oriented in ENE or nearly E-W directions with en echelon type, were derived from Weixinan boundary fault, and moved as normal faulting in Eocene and Oligocene, thus a dextral strike-slip fault system formed and controlled the development of fault and fissure belt in Weixinan area. In the influence of tectonic stress fields since Neogene, that fault system is generally trans-compression and relatively close.A lot of faults and fissures developed in the strata of Weixinan area, with stronghydration and anisotropic, the mudstone layers in Second member of Weizhou formation and Second member of Liushagang formation are researched especially. The inhomogeneity of strata was studied in detail, particularly to research sedimentary lithofacies in each borehole, two plan views and 11 profiles based on seismic data. It was divided into 13 mediums with different strength in that area, and which is favorable to improve the precision of numerical modeling.Depending on comprehensive research, making the 3D estimated modeling for tectonic stress and considering the condition of inclined borehole used logging data, the stress value was estimated in 17 boreholes and 18418.05 meters in length. Some rock mechanics parameters were also estimated, i.e. Young’s modulus (E) and Poisson ratio (v). The author combined the data of fault plane solution and diameter change of borehole wall and got the recent attitude of maximum principal compression stress was 320° Z5° in Weixinan region.Used the modeling parameters as similar as to real geological status, the modeling in two plan layers for project areas of 11-1N,11-4N and 12-1 and in 11 profiles were performed, and in which the estimated and modeling parameters of current tectonic stress field were well coincided, and also supported by the borehole history data. Then, the borehole wall stability was forecasted rather detail and some corresponding advices in drilling engineering were proposed, according to the modeling data of recent stress field and division of borehole wall stability belts.更多还原