四川长宁龙马溪组页岩气水平井钻井液防塌技术研究

发布时间：2018-04-27 19:30

本文选题：页岩 + 水平井　；参考：《西南石油大学》2015年硕士论文

【摘要】：水平井技术是页岩气勘探开发的关键技术之一,而水平井技术中的钻井液技术,尤其是稳定页岩气井壁的钻井液技术又是页岩气技术近年来的研究热点,是长期制约水平井成本和开发效益的核心和难点。页岩气水平井钻井过程中存在长水平段垮塌问题,多采用油基钻井液作为钻井液使用,但油基钻井液成本较高,影响到页岩气的开发钻井效益。本文针对长宁龙马溪易塌页岩地层,选取长宁地区龙马溪组露头页岩为研究对象,首先采用理化分析方法和X射线衍射分析了页岩的基本物性特征,然后对页岩的致塌机理结合岩石力学理论进行了分析,澄清了页岩封堵和抑制的防塌机理界限,提出了以封堵重力水和毛细水孔隙阻止静水压力传递的观点。实验研究了页岩矿物组成对黏土水化防膨规律的影响以及几大类页岩水化抑制剂抑制黏土晶层膨胀的规律,对页岩地层钻井坍塌压力进行了研究,建立以坍塌压力、坍塌周期优化钻井液的方法,包括优化钻井液成分、优化钻井液密度、优化钻井方位、优化长水平段的钻井周期等。通过对页岩致塌机理和防塌机理研究,取得了以下认识： (1)龙马溪页岩黏土矿物总量相对较低,主要以非膨胀矿物伊利石为主,含少量伊蒙混层,因此页岩的水化膨胀较弱,页岩存在软弱结构面和孔隙压力传递导致微裂缝扩展,页岩分散破裂,从而导致页岩整体强度降低才是破坏主因。 (2)页岩中水的存在状态有结合水和自由水两种形式,抑制解决的是结合水部分,封堵解决的只是自由水部分,自由水部分又包括重力水和毛细水,以0.1μm孔径为界限,小于0.1μm则毛细水不能通过,通过的只是结合水,结合水不能传递静水压力,因此从阻止静水压传递只要封堵能将页岩所有孔隙水转变成毛细孔隙水及界限以下的结合孔隙水即理论上能阻止静水压传递。 (3)页岩抑制剂的抑制能力与页岩中蒙脱石含量有关,大多数抑制剂随蒙脱石含量增加抑制能力减弱,硅酸钾的抑制能力不受蒙脱石含量的影响。 (4)页岩的层理结构和微裂缝发育使其岩石学和岩石力学特征呈现宏观和微观的弹性各向异性和强度各向异性,因此存在一个最优井斜穿越不稳定层。 (5)页岩的微裂缝通道是压力传递的主要通道,井周应力传递和传质传能过程中岩石强度降低使其存在一定的稳定周期,结合坍塌周期图版研究龙马溪易塌页岩地层坍塌周期,油基钻井液防塌周期较强抑制强封堵的水基钻井液防塌周期长,只有在防塌周期内通过该地层,并在最佳时间内完成完井任务。
[Abstract]:Horizontal well technology is one of the key technologies in shale gas exploration and development, and drilling fluid technology, especially drilling fluid technology for stabilizing shale gas sidewall, is a hot research topic in shale gas technology in recent years. It is the core and difficulty to restrict the cost and development benefit of horizontal well for a long time. During the drilling process of shale gas horizontal wells there exists the problem of long horizontal section collapse. Oil based drilling fluid is often used as drilling fluid but the cost of oil based drilling fluid is high which affects the drilling efficiency of shale gas development. In this paper, the outcrop shale of Longmaxi formation in Changning area is selected as the research object. Firstly, the basic physical properties of the shale are analyzed by physicochemical analysis and X-ray diffraction. Then, the collapse mechanism of shale is analyzed in combination with rock mechanics theory, and the limits of anti-collapse mechanism of shale plugging and restraining are clarified, and the viewpoint of blocking gravity water and capillary water pore to prevent hydrostatic pressure transfer is put forward. The influence of shale mineral composition on the hydration and anti-swelling law of clay and the laws of several kinds of shale hydration inhibitors inhibiting the expansion of clay crystal layer are studied experimentally. The drilling collapse pressure of shale formation is studied and the collapse pressure is established. The methods of drilling fluid optimization in collapse cycle include optimizing drilling fluid composition, optimizing drilling fluid density, optimizing drilling azimuth, optimizing drilling period in long horizontal section, etc. Through the study of shale collapse mechanism and anti-collapse mechanism, the following understandings have been obtained: (1) the total amount of clay minerals in Longmaxi shale is relatively low, mainly composed of non-expansive Illite with a small amount of immified layer, so the hydration expansion of shale is weak, and the shale has weak structural plane and pore pressure transfer, which leads to the microfracture expansion. The main cause of the failure is the scattered fracture of shale, which leads to the decrease of the overall strength of shale. (2) the existence of water in shale is in the form of combined water and free water, the inhibition solution is the binding water part, the plugging solution is only the free water part, the free water part includes gravity water and capillary water, and the limit is 0.1 渭 m pore size. If it is less than 0.1 渭 m, the capillary water cannot pass through, but only through the bound water, the combined water can not transfer the hydrostatic pressure, Therefore, the hydrostatic pressure transfer can be prevented theoretically by blocking all pore water in shale into capillary pore water and combining pore water below the limit. (3) the inhibition ability of shale inhibitor is related to the content of montmorillonite in shale. The inhibition ability of most inhibitors decreases with the increase of montmorillonite content, but the inhibition ability of potassium silicate is not affected by the content of montmorillonite. (4) the stratification structure and microfracture development of shale make its petrology and rock mechanics feature macroscopic and microscopic elastic anisotropy and strength anisotropy, so there is an optimal well crossing through unstable layer. (5) the micro-fracture passage of shale is the main channel of pressure transfer, and the rock strength decreases in the process of stress transfer and mass transfer energy transfer around the well, which leads to a certain stable period. Combined with the collapse cycle chart, the collapse cycle of the easily collapsible shale formation in Longmaxi is studied. The anti-sloughing period of oil-based drilling fluid is stronger than that of water-based drilling fluid with strong plugging. The anti-sloughing period of water-based drilling fluid is long and only passes through the formation during the anti-sloughing period and completes the completion task in the best time.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE254

【参考文献】