【作者】 郭春华；

【导师】 周文；

【作者基本信息】 成都理工大学 ， 油气田开发工程， 2011， 博士

【摘要】 须家河组气藏地处四川盆地西部川西深坳陷,油气富集,且近期滚动勘探开发取得了重大进展,展现出良好的增储上产前景,是西南油气分公司勘探开发研究院未来几年开发上主攻阵地。但是该地区地质条件复杂,地层温度高,属于深层异常高温、高压、低孔致密—超致密储层。地层岩性差异明显,砂泥岩频繁互层,天然裂缝发育,前期实钻资料显示该区钻井过程中复杂事故频发,常出现漏、塌、涌、卡等异常情况,影响钻进效率。同时针对储层非均质性强的特点,为提高裂缝钻遇率,该地区已经并正在进行水平井的试验开发,由于处于初期,井下复杂情况基本处于未知数,了解井壁失稳的影响因素,从而更好地掌握井壁稳定性技术,防止或预测井下复杂事故,是整个须家河组气藏勘探开发中非常重要的环节。鉴于此,本文以川西须家河组气藏为例,以数学、地球物理科学、地质学、力学、建筑学等多学科知识为理论指导,以数值模拟技术、计算机技术为手段,综合利用地震勘探、油气地质、油气钻井、地球物理测井等资料,深入分析工区岩石力学参数特征的基础上,较系统深入地开展研究区域地应力场模拟、直井和水平井在完整井壁及非完整井壁情况下井壁应力分布特征模拟及井壁稳定性分析研究,取得的研究成果及认识如下:(1)总结岩石力学参数特征研究基本方法的基础上,综合分析研究工区岩心室内实验资料及地球物理测井资料总结岩石力学静、动态特征,依据二者已有参数特征规律建立研究区岩石力学参数动、静态转换模型,并由此推算获得研究区未测岩石力学参数特征作为区域应力场模拟和井壁稳定性分析基础数据。(2)综合利用地应力直接测量和间接测量资料,考虑区域震源机制、断层构造活动特征的基础上,建立研究区目的层分岩性地质力学模型,用有限元数值模拟技术反演分析研究区域地应力场大小和方向的分布特征,并和其他方法获得的地应力特征作比较,获得研究区域目的层段地应力总体分布特征并以此为后面井壁应力分布提供原地应力状态。(3)依据已有的井壁应力分布计算解析算法为依据,探讨有限元分析井壁应力的可靠性,探索有限元模拟井壁应力的建模技术,建立不同井眼轴线轨迹、不同裂缝井壁特征模型。(4)以目的层远地应力为基础,建立直井(完整和非完整)井壁应力分布模型,计算不同情况下井壁应力值的大小,寻找井壁应力分布规律,与已有计算方法作对比,从力学上讨论分析直井(完整和非完整)井壁稳定性。(5)以数学、弹性力学理论为基础,建立大斜度井(包括水平井)三维井壁应力分布数学及力学模型,建立水平井(完整和非完整)井壁应力分布模型,计算不同情况下井壁应力值的大小,寻找井壁应力分布规律,与已有计算方法作对比,讨论分析水平井(完整和非完整)井壁稳定性。(6)系统归纳总结井壁稳定性判断力学准则,结合川西须家河深井钻探,综合测井解释、实钻资料和力学建模数值模拟分析方法,研究表明综合系统分析研究区域岩石力学特征、地应力分布特征及就地井壁应力分布特征,能有效地、系统性地开展井壁稳定性技术研究工作,为确保安全、高效钻井和压裂改造等提供强劲技术支持,此思路和方法对同类气藏开发具有借鉴意义。更多还原

【Abstract】 Great progress has been made in the exploration and exploitation of the Xujiahe Formation gas reservoir in recent years ,which is located in the west Sichuan depression. This reservoir is well known as typical tight pay zone with ultra high pressure and temperature, and the geological condition is quite complex. The distinct heterogeneous lithologic character ,such as the interbedding of sand and clay, along with nature fracture system, is the major reason to the frequent accidents ,which consists of leak, collapse ,kicking and sticking, and the drilling operation have been suffered much from this. To speed up the progress of gas reservoir exploitation, horizontal drilling operation have been introduced to put into pilot operation to improve the probability of disclosing nature fracture system as much as possible. At present, to get a better understanding of the safety complication and accident prevention, it is believed that the theoretical research on well bore stability could be the key factor, since few experience has been accumulated from actual horizontal drilling operation in this area. To take the Xujiahe gas reservoir as an example, based on the multidisciplinary knowledge from mathematics, geophysics, geology and civil engineering, by means of integrated approaches which consists of simulation and computation , the information from geophysics ,geology, drilling ,wire line logging and laboratory mechanics experiments are utilized to carry out the simulation on regional in-situ stress and the wellbore stability. The results can be listed as follows:1. Based on the primitive methods of rock mechanics ,the laboratory results and the wire-line logging data are utilized to summarize the static and dynamic mechanics parameters. The relationship deduced from laboratory mechanics parameters can be the basis to establish transformation model for this studied area, and can be the basic data for the regional stress field simulation and wellbore stability analysis. 2. The mechanical model has been built on the basis of joint application of various in-situ stress measurements, along with mechanism of earthquake focus and the distribution of fracture system. Taken into accounts of the different lithological belts , this model is solved by means of finite elements ,and the results of in-stitu stress are compared with that from on-site downhole measurements to show its accuracy . The general in-situ stress character of the target zone can be the basis for the further analysis of the stress distribution near-wellbore.3. Compared with the traditional analytic method for in-situ stress near wellbore, the feasibility of finite elements is proved. Herein , different models have been established to specify the unique character of various well bore axis, and the fractures cutting wellbore .4.Based on the global in-situ stress distribution of Xujiahe Formation, the calculation of in-situ stress near wellbore for vertical well is discussed ,the results of which could be adopted to interpret the different model of in-situ stress distribution .The results herein are also brought forward to justify the well bore stability for vertical well ,which could be proved by traditional analytic methods.5.Taken into account of elasticity theory, the mathematical models of in-situ stress near well bore for high inclination well , including horizontal well, are established, and the results from which could be utilized to deduce the in-situ stress distribution for different kinds of engineering conditions. The results herein are also brought forward to justify the well bore stability for high inclination well ,which could be proved by traditional analytic methods.6.Combined with deep well drilling operation in Xujiahe Formation of western Sichuan depression, well log interpretation, on-site drilling data , numerical simulation of mechanical modeling, the mechanical criteria for the borehole stability is systematically summarized. It is showed by this research listed herein that the regional mechanical characteristics, in-situ stress distribution in the pay zone or near wellbore can be useful for the research on borehole stability effectively and systematically, and can be strong technical support for the drilling and fracturing operation. All of the ideas and methods could be applicable to the similar gas reservoir home and abroad .更多还原