新站油田地应力研究与应用

大庆长垣西部新站油田属于特低渗透裂缝型油藏.油田注水开发主要矛盾是油井见水早、含水上升快、产量递减快,并且见水井没有明显的方向性,注采系统调整难度大,油田稳产难度大.为此,通过井壁崩落、微地震、波速各向异性等方法,对新站油田地应力进行研究,搞清了新站油田现今最大水平主应力方向主要为NE71.4°～100°,近东西向,从而明确了新站油田裂缝发育方位.应用地应力研究结果,新站油田宜采用矩形五点法或菱形反九点法注采井网注水开发,近东西向和南北向的油井要慎重压裂.     

利用成像测井技术识别钻井诱导缝

钻井诱导缝系钻井过程中产生的裂缝,钻井诱导缝的最大特别是沿井壁的对称方向出现呈羽状或雁列,但是有些诱导缝与人工裂缝却很难区分。本文总结了诱导缝的类别及其产生原因并利用FM I测井资料去识别钻井诱导缝,对碳酸盐岩储层的勘探和开发很有意义。     

三维岩体随机结构面切割方法

三维岩体随机结构面切割及块体分析是块体理论的新发展,成为边坡工程和地下洞室围岩稳定分析的有效手段。通过生成三维岩体随机结构面网络,将结构面相互切割,生成新的面,运用面的回路方法形成块体,然后确定岩体开挖面上的可动块体并找出关键块体。经多次模拟,可以获得岩体开挖面形成的关键块体几何形状和尺度规模等统计特征,为工程系统支护方案提供较可靠的设计依据。     

无充填周期性裂缝岩体的等效渗透系数（稿件编号：201600412）

为了研究无充填周期性裂缝岩体的渗流特性,建立了地下水流动分析模型,该模型假定裂缝和岩石交界面流速相等且剪应力连续。根据分析模型的边界条件,耦合Navier−Stokes方程和Brinkman-extended Darcy方程,推求出裂缝和岩石中水流的流速分布。结合线性Darcy定律,推导出无充填周期性裂缝岩体沿裂缝方向等效渗透系数的理论表达,该表达式揭示裂缝开度对等效渗透系数起控制作用。为进一步验证理论模型推求的成果,研制试验装置开展渗流试验。试验时用浇筑混凝土模拟岩石,用混凝土间缝隙模拟岩石裂缝。测得的平均渗透系数和理论计算得到的等效渗透系数在同一量级,且相差很小。试验结果验证了所推求等效渗透系数表达式的正确性和可靠性。     

JZS低潜山带储集层特征及控制因素分析

JZS低潜山带油藏是渤海油田勘探的又一次重大发现。通过采取岩心观察、薄片鉴定、扫描电镜、测井综合评价、应力场分析等岩性及裂缝研究方法指出JZS太古界潜山带储层为一套结晶岩,以斜长片麻岩、二长片麻岩为主,储集空间包括裂缝和溶蚀孔隙,裂缝在整套潜山储层中相当发育,其中构造高角度缝占主导地位,裂缝发育优势方位为北东~南西向、北北西~南南东向。储层发育受到岩性、构造运动、古风化溶蚀作用、充填物的影响。潜山储层的分布具有纵向分带,横向分区的特点,纵向上分为4个亚带,油气富存在前两个亚带,有效储层厚度为不整合面以下平均150~200m,风化壳顶0~5m,不作为主要产能区。     

测井技术在致密储层裂缝识别中的应用

测井方法是目前识别和探测致密储层裂缝最常用、最有效的方法。常规资料中的双侧向测井可以对裂缝的张开度、孔隙度、渗透率进行定量估算。应用FMI成像测井资料可以确定裂缝层,定量计算裂缝走向和倾角,判断天然有效裂缝发育状况及诱导缝的产生程度。常规资料与成像等新测井技术结合,能够更直观准确的指示裂缝,使裂缝性致密储集层的解释精度大为提高。     

Transverse drilling-induced tensile fractures in the West Tuna area, Gippsland Basin, Australia: implications for the in situ stress regime

Drilling-induced tensile fractures (DITFs) have been interpreted on image logs from vertical wells in the Gippsland Basin, offshore southeastern Australia. Interpreted axial (vertical) DITFs have previously been well described worldwide. We also interpret transverse (horizontal) DITFs, which are horizontal fractures that are electrically conductive, non-planar, bimodal and constrained to the tensile region of the wellbore.Elasticity theory predicts formation of both transverse and axial drilling-induced tensile fractures (DITFs) in vertical wells depending on the magnitude of the principal in situ stresses, pore-pressure and mudweight. Drilling-induced tensile fractures initiate in very specific stress environments. Axial DITFs can closely constrain a lower bound to the maximum horizontal stress (S_H max) magnitude where the minimum horizontal (S_h min) stress is known. If transverse DITFs are observed, they can constrain a lower bound to maximum and minimum horizontal stress magnitudes. The observation of transverse DITFs on image logs can constrain the stress field to one on the border of strike-slip and reverse faulting () without requiring knowledge of the S_h min or S_H max magnitude. The observation of transverse DITFs in the West Tuna area combined with wireline log data, leak-off tests and pore pressure data are used to constrain the in situ stress tensor. The interpreted in situ stress tensor lies on the border of a strike-slip and reverse faulting regime (S_H max40.5 MPa/km>S_h min≈S_v21 MPa/km). Interpreted data from leak-off tests in the West Tuna area confirm that S_h minS_v.     

Models for normal fracture deformation under compressive loading

A new semi-empirical model that can be used to predict fracture deformation behavior under normal compressive loading is presented. The development of a simple exponential model is presented first after which a modified and more general exponential model, with an additional degree of freedom in the model parameters, is obtained. The simple and the modified exponential models are then compared to available fracture closure models, namely the empirical Barton–Bandis hyperbolic model, and a power-law model based on Hertzian contact theory, to determine how good they fit the results of fracture closure experiments under monotonically increasing normal compressive loading. A new parameter called the half-closure stress, σ_1/2, is introduced and is used, in addition to the maximum fracture closure, Δv_m, in the model fitting procedures for the Barton–Bandis and the simple exponential model. The half-closure stress is shown to be related to the initial normal stiffness, K_ni, used in the original Barton–Bandis model. An additional parameter, n, is used in fitting the modified exponential model to the experimental data. Of the models presented herein, the modified exponential model was found to provide the best fit to the experimental data, for the same values of σ_1/2 and Δv_m, over the entire range of compressive stresses. The power-law model based on Hertzian contact theory was found to be unsuitable for predicting normal fracture deformation behavior.     

大柳树水利枢纽坝区松动岩体的水力学特性

黄河大柳树水利枢纽坝区岩体大范围发生了松动,确定其水力学特性指标并进行渗流分析具有重要的现实意义。首先,根据坝区两岸众多平硐和过河平硐资料,统计出两岸和坝基岩体的优势节理裂隙组参数分布,采用等效连续介质渗流理论,求出两岸和坝基岩体的渗透系数张量;然后依据坝区左岸固结灌浆试验(包括压水试验)资料和过河平硐实测渗水量资料,对渗透系数张量进行修正;最后,进行3个重要断面的渗流分析。可以看出：坝区工程范围内岩体渗透性很强,渗透系数张量量级达10^-5～10^-4m/s;绕坝渗流量大,帷幕灌浆工程量大。