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1.
Analysis of Pore Pressure and Stress Distribution around a Wellbore Drilled in Chemically Active Elastoplastic Formations 总被引：4，自引：1，他引：3
Drilling in low-permeable reactive shale formations with water-based drilling mud presents significant challenges, particularly
in high-pressure and high-temperature environments. In previous studies, several models were proposed to describe the thermodynamic
behaviour of shale. Most shale formations under high pressure are expected to undergo plastic deformation. An innovative algorithm
including work hardening is proposed in the framework of thermo-chemo-poroelasticity to investigate the effect of plasticity
on stresses around the wellbore. For this purpose a finite-element model of coupled thermo-chemo-poro-elastoplasticity is
developed. The governing equations are based on the concept of thermodynamics of irreversible processes in discontinuous systems.
In order to solve the plastic problem, a single-step backward Euler algorithm containing a yield surface-correction scheme
is used to integrate the plastic stress–strain relation. An initial stress method is employed to solve the non-linearity of the plastic equation. In addition, super convergent patch recovery is used
to accurately evaluate the time-dependent stress tensor from nodal displacement. The results of this study reveal that thermal
and chemical osmosis can significantly affect the fluid flow in low-permeable shale formations. When the salinity of drilling
mud is higher than that of pore fluid, fluid is pulled out of the formation by chemical osmotic back flow. Similar results
are observed when the temperature of drilling mud is lower than that of the formation fluid. It is found that linear elastic
approaches to wellbore stability analysis appear to overestimate the tangential stress around the wellbore and produce more
conservative stresses compared to the results of field observation. Therefore, the drilling mud properties obtained from the
elastoplastic wellbore stability in shales provide a safer mud weight window and reduce drilling cost. 相似文献
2.
井壁失稳是钻井过程中常常遇见的难题之一,尤其在钻遇泥页岩井段。针对河南中牟页岩气区块在山西组-太原组泥页岩钻进过程中发生井壁坍塌掉块、卡钻、井径扩大率大等复杂情况,利用MY1井钻井岩心从泥页岩类型划分、孔渗特征、微观结构、岩石力学以及地应力等方面开展井壁稳定性影响因素实验分析。通过分析可知,中牟区块泥页岩属硬脆性泥页岩,造成井壁失稳的主要因素为地层非均质性强,岩石脆性程度较高,微裂缝发育,易导致井壁机械剥落、坍塌掉块。通过合理控制钻井液密度、优化井身结构及钻井参数、研发低自由水强封堵钻井液提高井壁稳定性,在区块钻井实践中取得了较好的应用效果,基本解决了井壁失稳难题。 相似文献
3.
《Geomechanics and Geoengineering》2013,8(3):178-184
ABSTRACTWellbore instability is one of the major challenges facing the drilling industry and it shows itself in the form of wellbore collapse and/or fracture. The major reason for this challenge is the inability of the mud density to balance the weight of the excavated materials. While most drilling operations are carried out through shale formations, the complexities of drilling such wells are increased because of the tendency for shale to react with water-based mud. Moreover, the very low permeability of shale means that time-dependent effects may set in. The convention used to incorporate time-dependent effect is to couple the constitutive stress model and chemical diffusion, but in this study, we considered the effect of incorporating time variable into the rock failure criterion. The choice criterion used is the Mogi-Coulomb rock failure criterion, which was modified to incorporate the time effect. The results indicate that in an open-hole the mud density to prevent wellbore collapse increases with time while that to prevent wellbore fracture decreases, thus making the mud window reduce with time. 相似文献
4.
Jun-Liang Yuan Jin-Gen Deng Qiang Tan Bao-Hua Yu Xiao-Chun Jin 《Rock Mechanics and Rock Engineering》2013,46(5):1157-1164
Serious wellbore instability occurs frequently during horizontal drilling in shale gas reservoirs. The conventional forecast model of in situ stresses is not suitable for wellbore stability analysis in laminated shale gas formations because of the inhomogeneous mechanical properties of shale. In this study, a new prediction method is developed to calculate the in situ stresses in shale formations. The pore pressure near the borehole is heterogeneous along both the radial and tangential directions due to the inhomogeneity in the mechanical properties and permeability. Therefore, the stress state around the wellbore will vary with time after the formation is drained. Besides, based on the experimental results, a failure criterion is verified and applied to determine the strength of Silurian shale in the Sichuan Basin, including the long-term strength of gas shale. Based on this work, horizontal well borehole stability is analyzed by the new in situ stress prediction model. Finally, the results show that the collapse pressure will be underestimated if the conventional model is used in shale gas reservoirs improperly. The collapse pressure of a horizontal well is maximum at dip angle of 45°. The critical mud weight should be increased constantly to prevent borehole collapse if the borehole is exposed for some time. 相似文献
5.
针对沁水盆地煤层气钻井中存在的井壁稳定技术难题,采用X射线衍射、扫描电镜、泥页岩膨胀实验、页岩分散实验测试了泥页岩和煤岩体的组构及理化性能,分析了井壁失稳机理。依据"多元协同"防塌原理,研选出了高效包被抑制剂、封堵防塌剂和活度平衡剂,构建了泥页岩地层防塌钻井液体系QSFT和煤层钻开液QSMZ。评价结果表明,QSFT体系的粘度、切力适中,滤失量低、泥饼薄,对200 μm裂缝的封堵承压能力达3.0 MPa;QSFT和QSMZ具有较强的抑制水化能力,并能显著增加岩样单向抗压强度,对煤岩体岩心湿测渗透率的损害均低于30%,干测渗透率恢复值达到95%以上,可作为沁水盆地煤层气井的钻井液和储层钻开液。 相似文献
6.
A Fully Coupled Chemo-Poroelastic Analysis of Pore Pressure and Stress Distribution around a Wellbore in Water Active Rocks 总被引：1，自引：0，他引：1
Water active rocks consist of minerals that hold water in their crystalline structure and in pore spaces. Free water from
drilling fluid can be attracted by the formation depending on the potential differences between pore space and drilling fluid.
The fluid movement into the formation or out of the formation can lead to a change in effective stress, thus causing wellbore
failures. In all previous studies it is found that the solute transport from or to the formation is primarily controlled by
diffusion process and the effect of advection on solute transfer is negligible for a range of very low permeable shale formations
(>10−5 mD). In this study a range of permeable shale formations (10−5 to 10−3 mD) commonly encountered in drilling oil and gas wells are considered to investigate the solute transfer between drilling
fluid and formation due to advection. For this purpose a finite element model of fully coupled chemo-hydro-mechanical processes
was developed. Results of this study revealed that the solute transfer between the drilling fluid and the shale formation
is controlled primarily by permeability of the shale formations. For the range of shale formations studied here, there exists
a threshold permeability below which the solute transfer is dominated by diffusion process and above which by fluid in motion
(fluid flow). Results from the numerical experiments have shown that when the permeability of shales is greater than this
threshold permeability, the chemical potential gradient between the pore fluid and drilling fluid reaches equilibrium faster
than that when the permeability of shales is below this threshold value. Also it has been found that when advection is taken
into account, effective radial and tangential stresses decrease around the wellbore, particularly near the wellbore wall where
the solute concentration has reached near equilibrium. 相似文献
7.
页岩气主要以吸附和游离状态贮藏在海相、陆相和海陆过渡相泥页岩中,这些岩石的沉积过程、时间和类型不同,表现出了地层或岩石的物理化学性质各向异性的特点。页岩气钻探所遇地层主要是不同时代的泥岩、砂岩、泥质砂岩、砂质泥岩等,这些岩石对钻井液中水分子具有极强的敏感性。所以,在钻探过程中常遇到起下钻遇阻、孔内沉渣多、重复破碎、卡钻等问题,由此花费大量的时间处理,从而减少了纯钻时间。这些问题的根本原因则是由于岩石膨胀缩径、孔壁崩塌超径所造成的。本文首先对河南中牟页岩气区块地层特征进行了描述,并就牟页1井钻探问题从钻孔缩径和超径2个方面进行了理论研究和分析,最后从钻井液和钻探工艺选择方面提出了原则性的建议。 相似文献
8.
钻井液在页岩钻探中对维护孔壁稳定十分重要,其滤失形成的泥饼对保护储层同样有着举足轻重的作用。为了研究页岩岩粉侵入低固相钻井液中对泥饼基本性能的影响,选取湘西北硅质页岩岩粉为研究对象,通过正交试验设计并对结果进行了极差分析和方差分析。研究结果表明:岩粉的含量是影响泥饼厚度的主要因素;影响泥饼韧度的主要因素为滚动时间以及岩粉的粒径;质量分数为6%的200目岩粉在滚动6 h后形成的泥饼最薄;150目的岩粉在质量分数为6%时滚动12 h后形成泥饼的韧度最大;级配为（200+100）目时,质量分数为2%的岩粉滚动24 h后形成泥饼最薄;级配为（200+150）目时,质量分数为4%的岩粉在滚动12 h后形成泥饼韧度最大。研究结论对钻井液现场的固相控制有积极意义。 相似文献
9.
福建煤田地质构造复杂,断层发育,岩层极其破碎且较松软,泥岩受挤压破碎为薄片状或烂泥状,给钻探施工造成许多困难,比如泥页岩水化膨胀,孔壁失稳导致孔内坍塌严重等。采用绳索取心技术,优选金刚石钻头,科学确定泥浆配比和钻进参数,成功解决了这些孔内技术难题,提高了钻探效率,降低了生产成本,取得的施工经验可供该矿区或该类地层的钻探施工借鉴。 相似文献
10.
北部湾盆地涠西南油田群是南海西部重要的原油产区，同时油田群紧邻众多国家级自然保护区，属于环境敏感区域。针对北部湾盆地涠西南地区环保要求，以及涠洲组和流沙港组钻井过程经常出现井壁失稳导致的憋卡、起下钻阻卡等问题，开展了涠西南地区地层泥页岩特性及环保钻井液技术研究。通过地层岩石黏土矿物分析、孔喉结构分析以及理化性能评价，明确了涠西南地区泥页岩井壁失稳的机理；提出以类油基的水溶性复合基基液为核心，构建了一套具有油基钻井液工程特性和水基钻井液环保特性的新型环保防塌钻井液技术，并进行了相关的现场应用。现场应用显示：应用井与邻井相比，12-1/4″井段阻卡划眼时间减少，井径扩大率大幅度降低，并且在128 h的长时间浸泡过程中没有复杂情况产生，有效地解决了涠洲组、流沙港组易失稳地层的井壁稳定问题；同时，钻井液环保性能达到一级海域环保要求，可以替代目前应用的油基钻井液体系，解决了海上使用油基钻井液存在配制成本高、含油钻屑需全回收及环境危害隐患大等技术难题。该研究对于涠西南油田环保、井壁失稳和钻井液技术发展具有较高的理论价值和借鉴意义。 相似文献
11.
盐岩在深部高温高压环境下具有很强的蠕变特性,在岩盐层钻井经常出现井眼缩径、卡钻等复杂事故。目前关于岩盐层井段安全钻进泥浆密度的计算方法主要适用于均匀地应力的情况,难以在非均匀地应力条件下应用。为此研究建立了三向地应力作用下盐岩和砂泥岩相互交错的复合岩盐层井眼蠕变缩径的三维有限元模型,并以塔里木油田羊塔克地区深井为例,研究了非均匀地应力条件下,复合岩盐层井眼随时间变化的蠕变缩径规律,得出了一定泥浆密度下岩盐层井眼在不同时刻的井径值。计算结果表明,安全泥浆密度有限元模拟值与羊塔克地区岩盐层井段实际采用的安全泥浆密度非常接近,验证了所建数值模型的合理性和计算结果的可靠性,研究成果为岩盐层井段的安全钻进提供了技术支撑。 相似文献
12.
叶舞凹陷ZKX井位于叶县盐田范围内,该钻探的目的是河南叶舞凹陷盐矿的普查,该井设计井深2630 m,在2000～2400 m连续取心,主要钻遇以泥页岩、砂岩、含盐膏层及盐岩为主的沉积岩地层,钻进过程中存在防塌、护心、井壁稳定等方面的问题和难点。针对ZKX井的钻井难点,在钻井液体系优化的基础上,根据不同地层分别采用了防塌钻井液体系、欠饱和盐水钻井液体系和饱和盐水钻井液体系,解决了水敏性泥页岩钻进的防塌及盐岩地层连续取心的钻井液技术难点,探索出了一套适用于盐膏层取心钻进的低成本钻井液技术思路。 相似文献
13.
空气潜孔锤钻探工艺在基岩地区已是首选的一种技术。传统观念认为空气潜孔锤钻进工艺适用于坚硬岩石（硬、脆、碎地层）,在松散地层中则需要常规泥浆回转钻进或冲击钻进。通过典型松散地层的试验证明：空气潜孔锤在松散覆盖地层中可以实现正常的钻进,并且具有效率高、成本低、劳动强度小等优点,在粘土和潮湿粘土地层中钻进效率最高可达87和72 m/h。为解决页岩气、地热、煤层气、地下水等能源资源勘探时上覆地层的开孔或一开钻进提供了行之有效的方法,同时,也解决了缺水地区或严重漏失地层钻井液用水困难和传统开孔或一开泥浆回转钻探工艺复杂等问题。 相似文献
14.
15.
Seyed Morteza Mirabbasi Mohammad Javad Ameri Habiballah Zafarian-Rigaki Iman Rahimzadeh-Kivi 《Arabian Journal of Geosciences》2016,9(3):235
Shale formation swelling is one of the main factors affecting wellbore instability and associated problems in drilling operation. In order to eliminate these problems, it is important to investigate formation characteristics and understand mechanisms of rock-fluid interaction, from chemical/mechanical point of view. Shale membrane efficiency is known as an important parameter affecting wellbore instability. In order to measure this parameter, many mathematical models and experimental efforts have been carried out which consider mechanical-chemical processes for rock-fluid interactions. In this study, the field equations governing the problem have been derived based on the linear chemo-poroelastic theory and solved using analytical/numerical methods. Afterward, a comprehensive workflow to characterize the chemo-poroelastic parameters of illite-rich shale is conducted in the laboratory. In fact, mineralogical and apparent properties of shale sample have been described and some setups were performed such as triaxial test and membrane efficiency. Then genetic algorithm has been applied to solve an inverse problem and get a match between experimental data and modeling results. Ultimately, the three important properties in shale-fluid interactions, i.e., shale membrane efficiency, hydraulic, and chemical diffusivity coefficient have been estimated. Comparing the simulation results with the experimental data indicates that the simulation model can appropriately simulate the pore pressure transmission test. With this approach, the required parameters can be estimated with good accuracy without using time-consuming and costly tests. 相似文献
16.
Lloyd M. Wenger Cara L. Davis Joseph M. Evensen James R. Gormly Paul J. Mankiewicz 《Organic Geochemistry》2004,35(11-12):1527
Evaluation of petroleum-fluid properties, hydrocarbon shows, and source-rock characteristics requires new tools to properly recognize and correct for drilling and test-induced contamination, which is increasingly common in modern deepwater field operations. Oil exploration, development, and now production, are more frequently conducted in deeper-water environments where the challenges faced by drilling and operations can severely impact the evaluation of oil and rock geochemistry and fluid properties. Poorly consolidated sediments, swelling clay minerals, and responses to evolving environmental regulations regarding offshore disposal of drill cuttings have resulted in the widespread use of enhanced mineral oil or synthetic-based muds. Also, water-based drilling fluids used in some deepwater operations contain additives that may impact fluid and rock geochemistry. For example, asphalt-based shale stabilizers are added to aid well-bore competency and prevent sticking drill pipe, and polyalkylated glycols are added to depress freezing temperatures and prevent the formation of gas hydrates in the drilling mud. Because these and other additives are often a significant component of water-based muds, they may affect the geochemical signature of fluids and rocks and alter fluid properties. Highly saline brines are another important source of contamination as they are used in completion fluids, water-wet muds, and are emulsified in oil-wet muds. Brine components impact metal contents of petroleum-fluid tests and complicate the determination of formation-water compositions. Despite potential problems introduced by these additives, successful strategies can be devised to accurately access key geochemical and engineering parameters. 相似文献
17.
为研究一种离子稳定剂"ENI"对页岩气储层的护壁机理,以湘西北下寒武统牛蹄塘组炭质页岩为研究对象,通过抑制膨润土造浆试验、抑制页岩膨胀试验和抑制页岩分散试验,对比评价ENI作为钻井液关键处理剂的抑制性;通过扫描电镜试验考察ENI对炭质页岩细微结构的作用。试验表明:清水中加ENI后,膨润土造浆率降低52.41%,滚动回收率明显提高;提出的钻井液体系中,ENI钻井液作用下的页岩膨胀率最低,而滚动回收率最高,大于80%;同时,ENI生成的物质能填充孔隙,增强页岩颗粒间的连接。与所选用的其他处理剂相比,ENI具有更好的抑制炭质页岩水化膨胀、分散的效果,有助于维护井壁稳定。 相似文献
18.
Chuanliang Yan Jingen Deng Baohua Yu Wenliang Li Zijian Chen Lianbo Hu Yang Li 《Rock Mechanics and Rock Engineering》2014,47(6):2199-2209
In oil and gas drilling or geothermal well drilling, the temperature difference between the drilling fluid and formation will lead to an apparent temperature change around the borehole, which will influence the stress state around the borehole and tend to cause borehole instability in high geothermal gradient formations. The thermal effect is usually not considered as a factor in most of the conventional borehole stability models. In this research, in order to solve the borehole instability in high-temperature formations, a calculation model of the temperature field around the borehole during drilling is established. The effects of drilling fluid circulation, drilling fluid density, and mud displacement on the temperature field are analyzed. Besides these effects, the effect of temperature change on the stress around the borehole is analyzed based on thermoelasticity theory. In addition, the relationships between temperature and strength of four types of rocks are respectively established based on experimental results, and thermal expansion coefficients are also tested. On this basis, a borehole stability model is established considering thermal effects and the effect of temperature change on borehole stability is also analyzed. The results show that the fracture pressure and collapse pressure will both increase as the temperature of borehole rises, and vice versa. The fracture pressure is more sensitive to temperature. Temperature has different effects on collapse pressures due to different lithological characters; however, the variation of fracture pressure is unrelated to lithology. The research results can provide a reference for the design of drilling fluid density in high-temperature wells. 相似文献
19.
贵州地热井钻遇地层以灰岩和白云岩为主,夹杂泥岩、砂岩及煤层等不稳定地层,为满足井壁稳定及配合螺杆钻进工艺的需求,确定采用强抑制聚合物钻井液体系。通过正交试验确定了室内配方,并对配方的综合性能进行了室内测评。FT-1与QS-2协同作用可有效改善泥皮质量,白油润滑剂在1%加量时即可将润滑系数降低至0.2以下。其综合性能测试结果表明：该钻井液体系具有良好的流变性,抑制性强且润滑性良好。相比于无固相聚合物钻井液,井眼清洁能力明显增强,机械钻速提高了129%,漏失风险有所下降,取得了良好的实钻效果。 相似文献
20.
位于南海西部的莺歌海-琼东南盆地（下称:莺-琼盆地）具有井底压力与温度双高、安全作业密度窗口极窄等特点,在高温高压工况下引发钻井液流变性难以控制、井下恶性漏失、电测仪器阻卡和储层保护难度大等情况.因此,基于此区块复杂的地质条件,经过多次的室内试验研究,在常规聚磺高温高压水基钻井液的基础上,通过引入甲酸钾作为配方抑制剂,同时优选抗高温聚合物以及磺化钻井液材料,在提高了体系的抑制性同时,有效地降低了钻井液的活度,并且通过加重材料的优选,钻井液的流变性得到了改善,使得体系具有较低的高温高压滤失量,密度2.5 g/cm3的体系可以抗高温达240℃.现场实践表明,新型高温高压水基钻井液体系具有良好的抗高温性和流变性,较低的高温高压滤失量,优良的滤饼质量,同时根据电缆测井井壁取心结果,此新型水基钻井液体系的储层保护效果良好. 相似文献