Objective The maximum operating pressure for underground gas storage facilities designed for oil and gas reservoirs, both constructed and under construction in China, is currently set at the original formation pressure. There have yet to be successful cases of overpressure operation, which significantly impacts the economic benefits of converting depleted oil and gas reservoirs into underground gas storage facilities. This article aims to evaluate the maximum operating pressure and storage capacity of the Nanpu 1-29 gas storage facility from the perspective of the ultimate bearing capacity of cap layers and faults, with the goal of effectively enhancing the construction benefits of the facility. Methods The evaluation of the maximum operating pressure for the Nanpu 1-29 gas storage facility in eastern Hebei is based on the minimum principal stress measured in situ in the mining wells. Different effective porosity calculation methods are employed to quantitatively evaluate the effective storage capacity of gas and oil reservoirs, as well as the incremental capacity after pressure boosting operation, based on their development differences. Results The evaluation of the maximum operating pressure for the Nanpu 1-29 gas storage facility indicates that the minimum principal stress of the cap layers determined by the in-situ measurements in the mining wells is 34.00 MPa. Based on the tensile failure criteria determined by the minimum principal stress, the maximum operating pressure for the tensile failure of the cap layer is 27.20 MPa. Combined with the maximum safe injection pressure corresponding to shear failure of the cap layer (30.60 MPa) and the maximum safe injection pressure corresponding to unstable slip of the fault (27.60 MPa), the final maximum operating pressure for the Nanpu 1-29 gas storage facility is determined to be 27.20 MPa. Based on the effective storage capacity calculation model, considering factors such as the water content of the gas reservoir, residual water and edge porosity as well as the coefficient of influence, the efficiency of gas-driven fluid, and the utilization rate of oil-containing space, the maximum operating pressure increased from the original formation pressure of 22.50 MPa to 27.20 MPa. The practical storage capacity of the gas storage facility increased from 15.46×108 m3 to 18.14×108 m3, an increase of approximately 17.3%. Conclusion (1) The construction of gas storage facilities can be re-evaluated for the maximum operating pressure based on the minimum principal stress measured in situ in the mining wells, and overpressure design can be conducted under appropriate conditions. (2) Overpressure design can effectively increase storage capacity and improve the economic benefits of reservoir construction. Significance The research results have a certain reference value for the quantitative evaluation of the maximum operating pressure and storage capacity of other underground gas storage facilities, and are expected to significantly improve the economic benefits of overpressure-designed reservoir-type gas storage facilities in China.

In-situ stress is an important basic data for determining the top and bottom limit of operating pressure of underground gas storage, evaluating the stability of geological body and analyzing the fault activity in the storage area. Herein, the layered in-situ stress measurement method, test equipment and construction process of perforated interval were briefly introduced, and the minimum principal stresses of 2 reservoir sections and 3 mudstone caprock sections in the depth range of 4 150.0 m to 4 338.0 m of Well NP36-X in Pugu-2 Block of Jidong Oilfield were measured with this method. As shown by the results, the tests were repeated over 3 times for each section, and the fracture shut-in pressure in multiple tests had good consistency with the relative error less than 5%. Besides, the minimum principal stress in the mudstone caprock of Well NP36-X was determined to be 72.40 MPa to 74.27 MPa with various fracture shut-in pressure analysis methods. Moreover, the minimum principal stress of high permeability formation was comprehensively determined to be 54.89 MPa to 60.25 MPa with the fracture extension pressure and the injection flow. As an exploration based on the in-situ stress measurement method for the perforated interval of old wells, this method, especially the field application test based on the fracture extension pressure and the injection flow, can partly compensate the insufficiency that the classical in-situ stress measurement method of hydraulic fracturing is not applicable to the high permeability formation.

川南泸州地区为深层页岩气勘探的重点区,中生代以来经历了多期构造运动,下古生界五峰组—龙马溪组深层页岩储层的裂缝主要受控于区域古构造应力场.为了探究泸州地区有利的深层页岩勘探区,以其五峰组—龙马溪组深层页岩地层为研究对象,以褶皱断裂系统、地震资料综合解释、埋深古构造图和页岩岩石力学参数测试为基础,开展了目的层燕山期Ⅲ幕(裂缝主要形成时期)的古构造应力场数值模拟,采用ANSYS有限元数值模拟方法,结合钻井裂缝实测结果,利用裂缝形成的力学原理,预测了其裂缝发育特征.结果表明:该区深层页岩储层的地应力呈差异分布,燕山期Ⅲ幕最大主应力方向为NW向,约为135°;窄背斜核部和断裂附近裂缝发育,低陡构造向斜区裂缝较发育,宽缓向斜核部裂缝弱发育;主要发育水平层理缝和高角度裂缝,裂缝密度分布由NE向SW逐渐降低,在高应力值的低陡构造向斜区,深层页岩储层裂缝发育,有利于游离态天然气聚集.该结论为泸州地区深层页岩气的勘探开发提供了地质依据.

Accurately determining the stress state in deep shale reservoirs is the key to the efficient development of shale gas and other unconventional energy sources. An effective method to increase the evaluation and calculation accuracy of in-situ stress parameters in a deep shale reservoir is to combine different methods to obtain different stress information, such as obtaining the minimum horizontal principal stress based on the in-situ stress measurement, predicting the magnitudes of horizontal stress difference and the horizontal principal stresses by establishing the stress profile based on the rheological model, and estimating the direction of the maximum horizontal principal stress by the wellbore failure imaging logging. We applied this research idea to Well SZ1 in Hanzhong, Shaanxi Province. The minimum horizontal principal stress obtained by hydraulic fracturing ranged from 32 to 41 MPa; Then, the variation laws of rock rheological parameters with the depth were determined by the rock mechanical parameters obtained from cross-dipole acoustic logging data. And combined with the burial history of the reservoir and the strain rate of the crust, the stress profile of Well SZ1 was established. The results show that the magnitude of horizontal stress difference in the depth range of 1950~2025 m in the Niutitang Formation is between 10~15 MPa, and ranges of the minimum and maximum principal stresses are 28~41 MPa and 47~49 MPa, respectively. The predicted horizontal minimum principal stress values are in good agreement with the measured results. Based on the in situ stress measurement and predicted stress profiles, Well SZ1 is characterized by normal faulting (Sv > SH > Sh)or a combination of normal and strike-slip faulting regimes (Sv≈SH > Sh).The horizontal stress difference decreases with the increase of the gamma value, indicating that the stress profile has a good corresponding relationship with the formation lithology. Based on the distribution characteristics of borehole-induced tensile fractures recorded by imaging logging, the direction of the maximum horizontal principal stress in Well SZ1 is ~N74°W, which is consistent with the direction of the regional tectonic stress field. This study provides an important basis for accurately understanding the in-situ stress state of the target layer of Well SZ1, as well as the later horizontal well layout and fracturing control.

水平最小主应力是非常规油气储层压裂设计、压裂缝高控制和压裂后效果评价的重要基础数据.利用自主研发的深孔水压致裂原位地应力测试系统,对黔东南地区寒武系牛蹄塘组泥页岩储层进行地应力实测,获取深度1179～1188 m泥质粉砂岩层段水平最小主应力为24.9～25.3 MPa,1207～1208 m灰岩层段的水平最小主应力为21.4 MPa.结合公开报道的泥页岩储层地应力测量结果,定量评价泥页岩储层内水平最小地应力分布规律.结果表明:泥页岩储层内地应力明显受岩石的矿物含量控制,随着黏土等塑性矿物含量的增加,水平最小主应力明显增大;在区域构造应力场作用下,泥页岩层的水平最小主应力比砂岩或灰岩等脆性夹层高4～15 MPa;对于深层页岩气,应选择脆性矿物含量高的水平最小主应力低值区作为水平井穿行层段,不仅有利于压裂缝的起裂和扩展,且裂缝的闭合压力低,可有效避免支撑剂的破碎和嵌入,保持压裂缝的导流能力.

地应力大小和方向是干热岩开发中注采井网部署、水力压裂设计和诱发地震评估等方面的重要基础数据.本文利用非弹性应变恢复(ASR)地应力测试方法,实测获取了唐山市乐亭县马头营干热岩勘探区3～4 km深度范围的地应力状态.研究结果表明:①地应力量值随深度增加而加大,3139～3934 m深度范围内水平最小主应力介于59.0～90.7 MPa之间,水平最大主应力介于103.7～123.6 MPa之间.水平最大主应力方向介于N83°～114°E之间.②三向主应力总体表现为σH＞σv＞σh,表明研究区3～4 km深度构造应力占主导地位,该应力状态有利于走滑断层活动.③利用摩尔-库伦准则对邻区断层的稳定性进行分析,结果表明研究区3～4 km深度范围内的断层总体处于稳定的应力环境.④干热岩注水开发与断层稳定性分析表明,在统一的区域地应力场作用下,研究区3900～4000 m干热岩注水开发过程中,当地面持续注入压力达到或超过约28 MPa时,可能引起场区内断层的滑动失稳,导致中小地震的发生,在于热岩开发利用中需注意防范.研究结果对于唐山地区地球动力学研究及干热岩的开发利用具有一定的参考价值.

挡土墙是一种常见的岩土工程支护结构.为探索墙后填土泊松比变异性对挡土墙失稳概率的影响,首先在基于Lade-Duncan屈服准则的土压力计算公式和相关规范的基础上,推导了考虑墙后填土泊松比的挡土墙稳定性分析模型;然后将泊松比作为服从正态分布的随机变量,基于Monte Carlo法,提出了考虑墙后填土泊松比变异性的挡土墙失稳概率分析模型.通过算例分析表明:挡土墙稳定性系数随着墙后填土泊松比的增大而增大;当稳定性系数大于1时,填土泊松比变异性的存在使挡土墙仍存在失稳的可能,且变异性越强,墙体失稳概率越大;反之,当稳定性系数小于1时,泊松比变异性的存在使挡土墙存在保持稳定的可能性,且变异性越强,墙体保持稳定的概率越大.

Abstract The in situ stress state is a key parameter for shale gas exploration and geodynamics. To obtain the ultra-depth stress state of the Xuefengshan area, the hydraulic fracturing in situ stress method was employed in this study to determine the stress state at a depth range of 170–2021 m. The test results, which are the first reported for borehole depth greater than 2000 m in China, show that the magnitude of the in situ stress increases with the depth of the borehole. At a depth of 2021 m, the measured maximum and minimum horizontal principal stresses were 66.31 MPa and 43.33 MPa, respectively. The linear fitting relationships between the maximum and minimum horizontal principal stresses with the depth of the test borehole were SH = 0.033999D + 5.9996 and Sh = 0.020729D + 4.8058, respectively. In the borehole depth range of 170–800 m, the relationships of the three principal stresses were SH > Sh > SV, which is favorable for reverse faulting. At borehole depths of 1000–2021 m, the relationships changed to SH > SV > Sh, which implies that the deep stress regime of this area is strike-slip faulting.

地应力是非常规油气勘探开发中“甜点”评价、水平井部署和压裂设计的重要基础参数.目前国内外主要将基于弹性模型的常规储层地应力评价技术应用于泥页岩储层,未考虑流变特性对泥页岩储层地应力分布规律的影响,导致泥页岩储层地应力评价结果误差较大.为了提高地应力参数评价计算的准确性,提出了一种基于流变模型的地应力评价新方法(以下简称新方法),利用偶极声波测井数据获取的岩石力学参数,参考相关试验结果确定岩石流变参数随深度变化的规律,结合盆地埋藏史和地壳应变率,建立了贵州黔北地区安页1井地应力剖面.新方法评价得到的地应力值与小型压裂实测和应力多边形法确定的地应力值的对比分析结果表明:新方法预测的安页1井地应力剖面与实测结果吻合较好,并且其地应力评价结果与伽马测井结果也具有较好的对应关系,即随着黏土矿物或有机质含量的升高,水平主应力差变小.结论 认为,采用新方法得到的地应力评价结果更加符合于真实的地应力分布规律.

为了系统研究水压致裂测量中测试系统柔度的影响作用,利用新型水压致裂测试系统开展了现场试验.试验通过监测水压致裂测试过程中井口、压裂段和封隔器压力变化特征,分析了测试系统柔度对压裂参数和主应力的影响.结果 表明,测试系统柔度影响会造成井口的压裂参数Ps,Pr,Pb和SH值总体上大于压裂段对应结果.井口和压裂段的Ps,Pr,Pb,SH之间的绝对差值分布范围分别为0～0.375,0～0.75,0.125～0.875和-0.25～0.875 MPa,相对差值分布范围分别为0～5％,0～6％,0～4％和0～5％.Pb绝对差值除受测试系统柔度影响控制外,还受地层力学性质和地应力水平影响,而测试系统柔度影响Pr绝对差值机制复杂,需要进一步补充流量数据分析.同时,利用新型水压致裂测试系统,提出了准确获取关闭压力的新方法——关闭试验法.试验数据表明,关闭试验法能有效消除测试系统柔度和管路摩阻对Ps的影响,提高关闭压力结果准确性.使用压裂段压力数据、关闭试验方法能有效降低测试系统柔度和管路摩阻等对压裂参数和主应力结果的影响,而在仅使用井口压力数据时,建议对Ps,Pr,Pb和SH按照最大5％,6％,4％和5％的比例折减修正.

Current stress state data are important in underground mine construction, analysis the of tunnel stability, the forecasting of coal and gas rock bursts in underground mines. At present, the hollow inclusion gauge is primarily used for in situ stress measurement in underground mines. However, the sensors of these gauges often fail to fully adhere to the borehole wall, which can reduce the reliability of the measurement results. In this study, the anelastic strain recovery (ASR) in situ stress measurement method based on oriented cores is introduced. The effectiveness of this technique is analyzed by comparing the test results with those obtained by the hydraulic fracturing method. In addition, the reliability of the ASR method is evaluated by repeatability testing. The ASR results indicate a horizontal minimum principal stress error of less than 10% compared with those obtained by the hydraulic fracturing method. The repeatability test results show good consistency in the in situ stress measurement results of two back-to-back test samples. The ASR method is a safe and highly efficient technique that is not limited by the depth and measurement environment. Therefore, it is expected to have broad application for underground mine in situ stress measurement.

利用最新研制的深孔水压致裂地应力测量设备在雪峰山2000 m科钻先导孔内开展了原地应力测量,在孔深170～2021 m范围内获得了16个测段的有效地应力测量数据,是国内首次利用水压致裂法获得的孔深超过2000 m深度的原地应力测量成果.测量结果表明,地应力随孔深增加而逐渐加大,对实测数据进行线性回归,得到最大和最小水平主应力随深度变化的关系分别为:SH=0.03328H+5.25408,Sh=0.0203H+4.5662,在孔深2021 m深度,其实测值分别为66.31 MPa和43.33 MPa.基于实测数据,结合钻孔成像测试和井温测试结果,对测点应力状态进行了综合分析.在170～800 m深度范围,三向主应力关系为SH＞Sh＞Sv,有利于逆断层活动;孔深1000～2021 m表现为SH＞Sv＞Sh,表明该区域深部应力结构属于走滑型.最大水平主应力方向为北西—北西西方向.基于实测地应力数据及莫尔-库伦破裂准则,对测区附近断层活动性进行了分析讨论,认为该区域断层处于稳定状态.

介绍岩芯直径变形分析法(diametrical core deformation analysis,DCDA)的基本原理、基于激光测距仪的岩芯直径测试仪器和测试流程,并将该方法应用于松科2井6645～6846m深部地应力测试.研究结果表明:应力释放后的岩芯直径曲线均为正弦波型,呈π周期变化,且椭圆长轴和短轴近于正交,测试结果符合DCDA法理论结果,可反映原位地应力信息.岩芯截面椭圆长轴方向即水平最大主应力方向,结合岩芯黏滞剩磁定向结果,确定松科2井6645～6845m深度水平最大主应力方向为NE72°～83°;利用试验获取的岩芯弹性模量和泊松比,确定松科2井6645m水平主应力差约35MPa,6845～6846m水平主应力差约55MPa,与非弹性应变恢复法确定的结果吻合较好.DCDA地应力测试方法在松科2井6645～6846m的成功应用,为深部地应力信息的获取提供了新途径,特别是在超深或高温钻孔和地层较破碎的复杂地质条件下,应力解除法、水压致裂法等难以实施时,DCDA方法仍可获得较可靠的地应力数据.DCDA方法不受钻孔的深度和温度环境限制,只需要近均质且各向同性的圆柱岩芯,不需对岩芯进行切磨加工,有利于深部宝贵岩芯的重复利用.