【作者】 李家学；

【导师】 罗平亚；

【作者基本信息】 西南石油大学 ， 油气井工程， 2011， 博士

【摘要】 裂缝-孔隙发育地层,承压能力低,安全密度窗口很窄,导致井下容易出现井漏、溢流、井喷、坍塌等情况。怎样提高地层承压能力是本文研究的方向。本文首先研究了地层承压能力低的原因,发现了地层承压能力低与地层致漏裂缝和微裂缝发育有关。研究得出了裂缝开度在150微米以上就会产生漏失,漏失速度受裂缝开度、裂缝深度、裂缝宽度、压差、钻井流体排量、钻井流体粘度等因素影响。研究还发现裂缝的扩延与否取决于缝内流体压力。研究提出了提高地层承压能力的原理,一是堵漏浆必须对地层致漏裂缝进行有效的封堵,阻止其漏失并制止进一步扩大；二是堵漏浆必须及时有效的消除非致漏裂缝诱导作用,阻止非致漏裂缝诱导扩延而产生漏失。为此,本文提出了封缝即堵的钻井液堵漏技术,其机理为封堵剂在漏失量很少,很短时间内,在裂缝中架桥、填充,形成低渗透率、高强度的填塞层。由于填塞层的形成,钻井液从壁面渗滤出去而不能完全补充,裂缝诱导作用消失,裂缝不再被诱导扩延；填塞层能够承受井内流体压力、地层流体压力和缝面岩石闭合应力作用而不被破坏。根据机理优选了适合于封缝即堵技术的特殊的堵漏材料刚性颗粒封堵剂,此堵漏材料为惰性、高强度、颗粒状物质。通过室内实验,研究了刚性颗粒提高地层承压能力的效果。实验发现了一定量的刚性颗粒能够在很短时间内、很少漏失量的条件下,在地层模拟裂缝中形成渗透率很低的填塞层,且形成的填塞层能够承受5MPa以上的压力。从而验证了刚性颗粒能够实现封缝即堵,提高地层承压能力的要求。室内实验还验证了刚性颗粒抗高温、能酸溶、不与钻井液和地层流体反应,对钻井流体性能和录井等无较大的影响。在机理研究和室内实验研究的基础上提出了随钻封缝即堵技术、停钻封缝即堵技术的配方现场施工工艺,并在塔里木油田迪那地区、克拉玛依油田进行了多井次的现场试验。试验结果表明：使用随钻封缝即堵技术能提高地层承压能力,其实验井相比于邻井相同层位漏失量减少73.6%,漏失次数减少67%,停钻封缝即堵技术能提高实验井当量密度0.1g/cm3以上。在试验过程中完善了试验配方和工艺,形成一套完整的、可行的、有效的提高低承压地层承压能力的封缝即堵技术,为实现低承压地层安全、快速、高效钻进这一重大目标提供了理论支持和技术手段。更多还原

【Abstract】 The formation with fracture and pore have low resistance capacity and the narrow safety window of the drilling fluid density, which will make the complex situation of mud loss, overflow, blowout, and borehole collapse happen during the drilling. So how to enhance the resistance capacity of the formation is the purpose of this paper.This paper firstly analyzed the cause of low resistance capacity and found the key factor was the development of the leaking-fracture and micro-fracture in the formation. It come to the conclusion that when the wideness of fracture was more than 150 micro-meter, the leakage began to happen and the rate of mud loss was affected by the depth and wideness of fracture, operating pressure, the delivery volume, the viscosity of the drilling fluid and so on. It also come to the conclusion that whether the unleaking-fracture leakoff or not was dicided by the minimum principal stress.The theory of enhancing resistance capacity was advanced in this study. Firstly, the leak-fracture must be plugged effectively to stop loss and prevent the fracture being enlarged. Secondly, the loss control materials must eliminate timely and effectively the induction forse of the unleak-fracture and prevent the unleak-fracture enlarged and leakoff.Wherefore, this paper puts forward the technology of plugging fracture immediately. Its theory was that the fracture was bridged and filled up by the blockingagent and forming a layer in the fracture with low permeability and high intensity at short time and very small loss. The drilling fluid filtered out through the borehole wall not being completely supplied so as to make the induction forse in the fracture vanish with the result that the fracture was never enlarged any more.The blinding layer could resisted the drilling fluid pressure, the borehole pressure and the closure stress of the rock in fracture surface. According to the mechanism,the rigid particle, a kind of special inert intensive irregular granular material,was optimized suitable for the technology of plugging fracture immediately.The performance of rigid particles in enhancing the resistance capacity of formation was investigated by laboratory tests. It was found that a layer of low permeability could be form in model fracture using the rigid particlse with low loss and very short time, and the layer was able to bear a pressure of 5MPa or even higher. Therefore experiments showed that the rigid particles could exactly meet the requirement of plugging fracture immediately and improved the resistance capacity of formation. It was also confirmed that the rigid particles’resistance capacity had little influence by temperature, dissolved by acid, and not react with formation fluids or drilling fluids, and its have little influence on drilling mud and the well logging.On the basis of the mechanism research and experiments in laboratory, it is put forward that the plugging while drilling technology and the sealing loss on stop drilling technology, and it was tested for many times in DiNa area of Tarim oilfield and Kelamayi oilfield.The results showed that compared to adjacent wells, the loss volume was reduced by 73.6% and the number of leakage was reduced by 67% happening in the same layer in experimental wells where the technology of drilling and plugging fracture immediately was applied. With the sealing loss of stopping drilling, the equivalent circulating density of experimental wells could be improved by 0.1/cm3 or higher.It had formed the plugging fracture technology while drilling using rigid particles added to all the recycling process of mud, the drilling-in slugging technology of preventing and controlling loss, the technology of controlling loss after stopping drilling and the technology of controlling loss before well being cemented.In all, A feasible and effective technology, called enhance resistance capacity immediately, which formed by research、experiment and so on, provided us a theory and tool to achieve a major purpose of the safe, rapid and efficient drilling at the formation of low resistance capacity.更多还原