Rock mass response for lined rock caverns subjected to high internal gas pressure

The storage of hydrogen gas in underground lined rock caverns(LRCs)enables the implementation of the first fossil-free steelmaking process to meet the large demand for crude steel.Predicting the response of rock mass is important to ensure that gas leakage due to rupture of the steel lining does not occur.Analytical and numerical models can be used to estimate the rock mass response to high internal pressure;however,the fitness of these models under different in situ stress conditions and cavern shapes has not been studied.In this paper,the suitability of analytical and numerical models to estimate the maximum cavern wall tangential strain under high internal pressure is studied.The analytical model is derived in detail and finite element(FE)models considering both two-dimensional(2D)and three-dimensional(3D)geometries are presented.These models are verified with field measurements from the LRC in Skallen,southwestern Sweden.The analytical model is inexpensive to implement and gives good results for isotropic in situ stress conditions and large cavern heights.For the case of anisotropic horizontal in situ stresses,as the conditions in Skallen,the 3D FE model is the best approach.

Origin of abnormal high pressure and its relationship with hydrocarbon accumulation in the Dina 2 Gas Field, Kuqa Depression

Based on distribution of formation pressure by indirect estimation and formation testing,this study investigates origin of abnormal high pressure in the Dina 2 Gas Field in the Kuqa Depression in combination with the latest research findings.Contribution of major overpressure mechanisms to this gas field is estimated,and generation of the abnormal high pressure as well as its relationship with natural gas accumulation is explored.Disequilibrium compaction,tectonic stress,and overpressure transfer are the major overpressure mechanisms.Overpressure transfer resulted from vertical opening of faults and folding is the most important cause for the overpressure.Gas accumulation and abnormal high pressure generation in the reservoirs of the Dina 2 Gas Field show synchroneity.During the early oil-gas charge in the Kangcun stage,the reservoirs were generally normal pressure systems.In the Kuqa deposition stage,rapid deposition caused disequilibrium compaction and led to generation of excess pressure(approximately 5-10 MPa)in the reservoirs.During the Kuqa Formation denudation stage to the Quaternary,reservoir overpressure was greatly increased to approximately 40-50 MPa as a result of vertical pressure transfer by episodic fault activation,lateral overpressure transfer by folding and horizontal tectonic stress due to intense tectonic compression.The last stage was the major period of ultra-high pressure generation and gas accumulation in the Dina 2 Gas Field.

异常高压含水凝析气藏有效库容影响因素

有效库容是储气库的关键参数,有效库容评价影响储气库的功能定位、调峰规模、建库参数设计以及整体建库方案设计。异常高压含水凝析气藏改建储气库时,异常高压、水侵和反凝析现象影响库容。由于气藏异常高压,储气库设计上限压力为58.00 MPa,远低于原始地层压力,气体体积系数不同,储气库库容也不同;储气库注采运行过程中,水体往复运移对储集空间动用效率具有较大的影响;储气库交替注采过程中,当地层压力低于露点压力时,凝析油析出对库容有一定的影响。针对这一问题,研究建立了改进的物质平衡和数值模拟双模型,以气藏动态储量为基础,定量分析了异常高压、反凝析、水侵等因素对库容的影响,并建立了一套考虑多因素影响的储气库有效库容评价方法。该成果现场应用于轮南59石炭系气藏建库,准确评价了该储气库的有效库容,为轮南59石炭系气藏改建地下储气库建库参数研究奠定基础。

储气库井油套环空注保护液和氮气柱对比

为了有效解决地下储气库注采过程中管柱内外压力变化给管柱安全性带来的问题,针对地下储气库气井管柱注采过程中温度、压力的波动特征,采用热力学与传热学理论,根据环空注满保护液与环空注入一段氮气柱2种情况分别建立了储气库管柱内外压力平衡模型,分析计算了2种模型的管柱内外压力及变化差异,重点研究了环空注氮气柱的最佳长度,绘制了氮气柱长度与封隔器下入深度最佳组合图版。研究结果表明:相同条件下环空注氮气可将注采过程中环空压力减少50%~90%,最佳氮气柱长度为封隔器下深的1/20~1/15;氮气柱长度越长,环空压力值越低;油管流体温度、油管内压力的敏感性分析表明,温度对环空压力变化影响较大;油套环空里注入合理的氮气柱长度可以防止储气库井管柱破坏和封隔器失效。

异常高压弱水驱凝析气藏改建储气库库容量评价

在废弃的异常高压弱边水凝析气藏建立储气库,库容量评价面临动储量计算方法优选和实际有效孔隙空间评价的问题。在生产动态资料的基础上,采用考虑弱水侵异常高压物质平衡法、流动物质平衡法和Blasingame分析法等综合方法评价区块原有效孔隙体积;利用改进物质平衡法评价水侵量;通过等容衰竭实验、生产动态计算气藏反凝析液量,定量评价区块当前剩余有效孔隙体积;建立物质平衡注采动态预测模型,确定库容量大小。实践表明:研究区动储量为70.3×10^(8) m^(3),库容量为64.4×10^(8) m^(3),受水侵及反凝析影响,库容量与动储量相差约8%。该库容量评价流程及方法能够充分考虑气藏开发过程中造成储层有效孔隙空间变化的影响因素,为后续方案设计中准确评估库容量提供依据。

某高速柴油机试车过程中飞车故障原因分析

针对某船用高速柴油发电机组低负载运行时发生排温异常,在卸负载时发生飞车故障的问题,通过对柴油机燃油系统和配套设备的检查与分析,发现由于高压油泵卡滞使柴油机发生飞车故障,并实施了解决方案。

Petroleum geological characteristics of Kela-2 gas field

The Kela-2 gas field is located in the center ofKelasu structural belt in Kuqa Depression. This trap is oneof a series of traps in the folded belts which are distributed ina string of pearls in the dual structure. The primary gas-bearing layers are sandstone of Lower Cretaceous K1bswhile the secondary layers are dolomite member and gluten-ite member of Lower Tertiary E1-2km and sandstone ofLower Cretaceous K1b. The main component of natural gasis methane whose content is higher than 97%. It is charac-terized by dry gas whose source rock is Jurassic coal meas-ure. The Kela-2 structural trap was formed during the Xiyuperiod and then became a reservoir in the late time. The res-ervoir formed late and the thick seal rock of Lower Tertiarygipsmantle are the avail reason why the giant Kela-2 gasfield has been well kept. The abnormal high pressure of theKela-2 gas field results from the strong structural compres-sion in the northern part during the Xiyu period.

Experimental research on reservoir sensitivity to stress and impacts on productivity in Kela 2 Gas Field

Kela 2 Gas Field, with high formation pressure (74.35MPa), high pressure coeffi-cient (2.022) and difficulty of potential test and evaluation, is the largest integrated proved dry gas reservoir in China so far and the principal source for West-East Gas Development Project. In order to correctly evaluate the elastic-plastic deformation of rocks caused by the pressure decline during production, some researches, as the experiment on reservoir sensitivity to stress of gas filed with abnormal high pressure, are made. By testing the rock mechanic properties, porosities and permeabilities at different temperature and pressure of 342 core samples from 5 wells in this area, the variations of petro-physical properties at changing pressure are analyzed, and the ap-plicable inspection relationship is concluded. The average productivity curve with the reservoir sensitivity to stress is plotted on the basis of the research, integrated with the field-wide produc-tivity equation. The knowledge lays a foundation for the gas well productivity evaluation in the field and the gas field development plan, and provides effective techniques and measures for basic research on the development of similar gas fields.

异常高压枯竭气藏型储气库地质体四维地质力学分析——以西南X储气库为例

异常高压气藏开发阶段压力变化幅度较大,且其改建储气库后交变注采阶段上限压力无法达到原始地层压力,在其地质力学问题评价时,常规方法不适用,缺乏系统的评价技术。为了更好地保障异常高压气藏型储气库安全、高效的运行,以X异常高压枯竭气藏为对象,选取开发末期储层压力场和地质力学数值模拟得到的应力、应变场进行数据交互传递,建立圈闭地应力-储层渗流动态耦合模型,采用有限差分与有限元结合的方法,以储气库圈闭为基本评价单元,系统、准确地评价圈闭地质体的四维地质力学问题,形成异常高压枯竭气藏型储气库圈闭地质体四维地质力学问题评价技术,为同类气藏改建储气库后的地质力学问题评价提供技术支撑。