【作者】 王晓；

【导师】 周文；

【作者基本信息】 成都理工大学 ， 油气田开发地质， 2011， 硕士

【摘要】 川西坳陷深层须家河组天然气资源量巨大,具有广阔的勘探开发前景。然而须家河组气藏储层致密,能否获得高产在很大程度上取决于裂缝的发育程度。由于裂缝分布非均质性强、天然裂缝预测难度大和直井钻遇裂缝几率低等原因,使得川西坳陷须家河组气藏的开发存在极大的困难。为高效开发须家河组气藏,需要采用大斜度井或水平井等技术以提高裂缝钻遇率。目前,研究区目的层水平井开发才刚刚起步,尚缺乏可借鉴的成功经验,相关钻完井技术还有待攻关。因此,急需开展研究区目的层水平井井壁稳定性的研究工作,为合理开发须家河组气藏提供科学的技术支持。本文基于实测的横波时差测井资料,采用二项式拟合法获取了研究区横波时差数据。在此基础上,通过声波速度频散校正,筛选岩性、结构面、泥质含量和品质因子等参数,校正前人经验公式等方法确定了岩石的强度力学参数及弹性力学参数测井解释模型;并依据研究区模拟地层条件下的实测数据,分岩性建立了岩石动态和静态弹性力学参数的转换模型。本文综合多种测井资料,选用ADS法建立了研究区目的层单井地应力剖面。在综合考虑多种运用特殊测井资料解释地应力方向的方法及前人实验结果的基础之上,本文确定研究区目的层现今最大水平主应力为近东西方向。因为大斜度井井眼轨迹不再与垂向主应力重合,也不再与水平主应力正交,所以需通过坐标转换方法以建立大斜度井井壁围岩力学模型。本文结合该模型,选用Mohr-Coulomb准则及最大张应力破坏准则,分别讨论了不同地应力状态下坍塌压力和破裂压力随井周角、井斜角和井眼方位角的变化规律。本文开展了泥浆安全密度窗随最大水平主应力、内聚力和内摩擦角等地层特性参数的变化规律,并分析了泥浆安全密度窗随各参数的敏感性。在其他条件不变的情况下,泥浆安全密度窗随井斜角的增大而增大。在研究区实际地应力状态σH>σv>σh下,坍塌压力随最大水平主应力σH、孔弹系数η和地层孔隙压力Pp的增大而增大,坍塌压力随内聚力C和内摩擦角φ的增大而减小;破裂压力随最大水平主应力σH、孔弹系数η和地层孔隙压力Pp的增大而减小,破裂压力随抗张强度σt的增大而增大。由此可知,泥浆安全密度窗的范围随最大水平主应力σH、孔弹系数η和地层孔隙压力Pp的增大而减小,井壁岩石失稳的可能性增大。最后综合上述研究成果,本论文计算了X10-1H井水平段的泥浆安全密度窗,该计算结果与X10-1H井井下实际情况和地破压力实验结果相吻合。这表明,本论文所建立的研究区目的层水平井井壁稳定性研究方法科学可靠,可以有效指导研究区目的层下一步的油气勘探开发工作。更多还原

【Abstract】 The gas resource quantity of Xujiahe formation in west Sichuan is huge, and the exploration & exploitation prospects are good. Because the tight reservoir of Xujiahe formation, the yield is depending on the fracture development. Because of the heterogeneity of fractures、hardness of predicting natural fractures and low probability of encountering fractures, the gas development of Xujiahe formation in west Sichuan is very hard. In order to exploit the Xujiahe formation gas pool, the high angle deviated well and horizontal well should be used to increase the chance to meet the fractures. There are not many horizontal wells in Xujiahe formation, so drilling and completion technology is not mature. Now, it is urgent to study on the horizontal well borehole stability in order to provide technical support for the reasonable exploitation of gas resource of Xujiahe formation.On the base of true shear wave, this paper used the method of binomial fitting to calculate the shear wave of study area. On this basis, this paper used many ways to calculate the strength parameters and elastic parameter, such as, calibrating the sound wave frequency dispersion、selecting the lithology and quality factor and calibrating the empirical formula. On the base of experimental data, this paper established the separate relationship between the dynamic and static parameters for sandstone and mudstone.According to several kinds of well logging datas, this paper selected the ADS model to calculate the crustal stress of single well. On the basis of well logging interpretation and experimental results, the orientation of maximum horizontal principal stress is EW.Because the well track of high angle deviated well is not vertical and it is not orthogonal with the horizontal principal stress, the mechanical model of sidewall rock is needed. On the basis of this model, this paper used the Mohr-Coulomb criterion and the maximum tensile stress failure criterion to discuss the relationship between the safe mud weight and other parameters, such as, maximum horizontal principal stress、cohesion and friction angle. This paper also analyzed the sensitivity of these parameters. When the other parameters are not changed, the bigger deviation angle, the bigger safe mud weight. On the basis ofσH>σv>σh, when theσH、η、Pp increase, the collapse pressure also increase. When C andφdecrease, the collapse pressure also decrese. WhenσH、ηand Pp increase, the fracture pressure decrease. Whenσt increase, the fracture pressure also increase. It can be seen that the range of safe mud weight becomes smaller when theσH、ηand Pp increase. In this case, the sidewall rock is easy to be damaged.Finally, this paper used these research results to calculate the safe mud weight of horizontal section of X10-1H well. The calculation result coincides with the actual situation of X10-1H well and formation breakdown pressure.So, the study method about the horizontal well borehole stability of Xinchang Xujiahe formation in west Sichuan is reliable, and it can be used into the future exploration and exploitation of oil and gas resources of Xinchang Xujiahe formation in west Sichuan.更多还原