Heterogeneity and influencing factors of marine gravity flow tight sandstone under abnormally high pressure:A case study from the Miocene Huangliu Formation reservoirs in LD10 area,Yinggehai Basin,South China Sea

The characteristics of reservoir heterogeneity of the marine gravity flow tight sandstone from the Miocene Huangliu Formation under abnormally high pressure setting at LD10 area in Yinggehai Basin are studied,and the influencing factors on reservoir heterogeneity are discussed,based on modular formation dynamics test,thin sections,XRD analysis of clay minerals,scanning electron microscopy,measurement of pore throat image,porosity and permeability,and high pressure Hg injection,as well as the stimulation of burial thermal history.The aim is to elucidate characteristics of the heterogeneity and the evolution process of heterogeneity of the reservoir,and predict the favorable reservoirs distribution.(1)The heterogeneity of the reservoir is mainly controlled by the cement heterogeneity,pore throat heterogeneity,quality of the reservoir heterogeneity,and the diagenesis under an abnormally high pressure setting.(2)The differences in pore-throat structure caused by diagenetic evolution affected the intergranular material heterogeneity and the pore throat heterogeneity,and finally controlled the heterogeneity of reservoir quality.(3)Compared with the reservoir under normal pressure,abnormally high pressure restrains strength of the compaction and cementation and enhances the dissolution of the reservoir to some extent,and abnormally high pressure thus weakening the heterogeneity of the reservoir to a certain degree.The favorable reservoirs are mainly distributed in the gravity flow sand body under the strong overpressure zone in the middle and lower part of Huangliu Formation.

Productivity Analysis Method of Abnormal High-Pressure Gas Reservoir in Ying-Qiong Basin

Ying-Qiong Basin in the west of South China Sea contains plenty of abnormal high-pressure gas reservoirs, whose stress sensitivity is crucial for well productivity. To explore the influence of stress sensitivity on production, the variable outlet back pressure stress sensitivity experiments were applied to test core sample permeability under different burden pressure and obtain the relational expression of power function of core stress sensitivity. Afterwards, new productivity equation is deduced in consideration of reservoir stress sensitivity, and the affection of stress sensitivity on production is analyzed. The result demonstrates close link between stress sensitivity and productivity, since single well production decreases dramatically when reservoir stress sensitivity has been taken into account. This research is constructive for well-testing data interpretation in stress sensitive gas reservoirs.

Action mechanisms of abnormal fluid pressure on physical properties of deep reservoirs: A case study on Jurassic Toutunhe Formation in the southern margin of Junggar Basin, NW China

Considering the action mechanisms of overpressure on physical changes in skeleton particles of deep reservoir rocks and the differences in physical changes of skeleton particles under overpressure and hydrostatic pressure, the sandstone of the Jurassic Toutunhe Formation in the southern margin of Junggar Basin was taken as an example for physical modeling experiment to analyze the action mechanisms of overpressure on the physical properties of deep reservoirs. (1) In the simulated ultra-deep layer with a burial depth of 6000-8000 m, the mechanical compaction under overpressure reduces the remaining primary pores by about a half that under hydrostatic pressure. Overpressure can effectively suppress the mechanical compaction to allow the preservation of intergranular primary pores. (2) The linear contact length ratio under overpressure is always smaller than the linear contact length ratio under hydrostatic pressure at the same depth. In deep reservoirs, the difference between the mechanical compaction degree under overpressure and hydrostatic pressure shows a decreasing trend, the effect of abnormally high pressure to resist the increase of effective stress is weakened, and the degree of mechanical compaction is gradually close to that under hydrostatic pressure. (3) The microfractures in skeleton particles of deep reservoirs under overpressure are thin and long, while the microfractures in skeleton particles of deep reservoirs under hydrostatic pressure are short and wide. This difference is attributed to the probable presence of tension fractures in the rocks containing abnormally high pressure fluid. (4) The microfractures in skeleton particles under overpressure were mainly formed later than that under hydrostatic pressure, and the development degree and length of microfractures both extend deeper. (5) The development stages of microfractures under overpressure are mainly controlled by the development stages of abnormally high pressure and the magnitude of effective stress acting on the skeleton particles. Moreover, the development stages of microfractures in skeleton particles are more than those under hydrostatic pressure in deep reservoir. The multi-stage abnormally high pressure plays an important role in improving the physical properties of deep reservoirs.

Test and Study of the Rock Pressure Sensitivity for KeLa-2 Gas Reservoir in the Tarim Basin

KeLa-2 gas reservoir is the largest uncompartimentalized gas field so far discovered in China, with a reserve of hundreds of billions of cubic meters of dry gas. It has such features as extremely long interval (550m), high pressure (74.5MPa) and pressure coefficient (2.022). Gas reservoirs with a pressure coefficient of over 2.0 are not commonly found. The abnormal high-pressure reservoirs are quite different in characteristic and performance during the process of depletion exploitation. Therefore, it is necessary to know the property of pressure sensitivity for this abnormal high-pressure reservoir. The aim of this paper is to test the reservoir pressure sensitivity and to analyze its effect on the deliverability of gas. Through some experiments, the permeability change with the confining pressure of rock samples from KeLa-2 abnormal high-pressure gas reservoir is measured. A power function is used to match the measured data, and to derive an empirical equation to describe the change of permeability through the change of the reservoir pressure or effective overburden pressure. Considering the permeability change during the development of reservoirs, a conventional deliverability equation is modified, and the deliverability curve for KeLa-2 gas reservoir is predicted. The research indicates that the extent of the pressure sensitivity of rock samples from KeLa-2 is higher than that from the Daqing oilfield. KeLa-2 reservoir rock has the feature of an undercompaction state. The pressure sensitivity of a reservoir may decrease the well deliverability. It is concluded that for KeLa-2 reservoir the predicted absolute open flow (AOF), when the pressure sensitivity is taken into account, is approximately 70% of the AOF when permeability is constant and does not change with pressure.

基于AHP的高压燃气管道失效分析

高压燃气管道一旦发生失效,不仅泄漏量大,修复难度高,而且可能造成局部停气,造成不良的社会影响。本文从可能导致高压燃气管道失效的原因出发,通过层次分析法对造成管道失效的原因进行排序,并以此作好相应的预防措施。

Characteristics,origin and controlling effects on hydrocarbon accumulation of overpressure in foreland thrust belt of southern margin of Junggar Basin,NW China

Aiming at the differential distribution of overpressure in vertical and lateral directions in the foreland thrust belt in the southern margin of Junggar Basin,the study on overpressure origin identification and overpressure evolution simulation is carried out.Based on the measured formation pressure,drilling fluid density and well logging data,overpressure origin identification and overpressure evolution simulation techniques are used to analyze the vertical and lateral distribution patterns of overpressure,genetic mechanisms of overpressure in different structural belts and causes of the differential distribution of overpressure,and the controlling effects of overpressure development and evolution on the formation and distribution of oil and gas reservoirs.The research shows that overpressure occurs in multiple formations vertically in the southern Junggar foreland thrust belt,the deeper the formation,the bigger the scale of the overpressure is.Laterally,overpressure is least developed in the mountain front belt,most developed in the fold anticline belt,and relatively developed in the slope belt.The differential distribution of overpressure is mainly controlled by the differences in disequilibrium compaction and tectonic compression strengths of different belts.The vertical overpressure transmission caused by faults connecting the deep overpressured system has an important contribution to the further increase of the overpressure strength in this area.The controlling effect of overpressure development and evolution on hydrocarbon accumulation and distribution shows in the following aspects:When the strong overpressure was formed before reservoir becoming tight overpressure maintains the physical properties of deep reservoirs to some extent,expanding the exploration depth of deep reservoirs;reservoirs below the overpressured mudstone cap rocks of the Paleogene Anjihaihe Formation and Lower Cretaceous Tugulu Group are main sites for oil and gas accumulation;under the background of overall overpressure,both overpressure strength too high or too low are not conducive to hydrocarbon enrichment and preservation,and the pressure coefficient between 1.6 and 2.1 is the best.

准噶尔盆地深层-超深层碎屑岩致密气储层特征及其控制因素

为寻找准噶尔盆地深层-超深层有利碎屑岩致密气储层,利用钻井、录井、薄片及化验资料,研究了碎屑岩致密气储层发育特征、储集空间类型、物性变化特征及有利储层控制因素。研究结果表明:①深层-超深层有利碎屑岩致密气储层储集岩主要为三角洲砾岩和砂岩,以细砾(砂)岩、中砾(砂)岩及中-细砾(砂)岩为主,为岩屑类砂岩。砾石成分和砂岩岩屑以凝灰岩为主,胶结物主要为方解石,局部富集沸石类。②储集空间为孔隙和裂缝,以孔隙为主。储集空间有孔隙型、裂缝型和孔隙-裂缝混合型3种组合类型。孔隙主要为原生剩余孔隙和次生溶蚀孔隙,以次生溶蚀孔隙为主。裂缝以成岩压实微裂缝和构造裂缝为主。③碎屑岩致密气储层垂向上形成了3个次生孔隙发育带。④岩石成分、建设型成岩作用和异常高压是控制有利储层的主要因素,3个主要因素控制了盆地深层-超深层碎屑岩致密气有利储层的发育和分布。

海洋精细控压钻井技术现状及应用

随着勘探技术的进步,不断向深部地层钻进,溢漏同存、窄压力窗口、异常高压等问题突出,往往会发生喷漏卡塌等复杂情况,这些已成为安全高效钻探面临和急需解决的难题。针对上述突出问题,考虑国内海洋钻井相比陆上钻井在地质特征、井身结构、作业模式等方面的差异,以陆上精细控压装备结构及工艺原理为基础,攻关形成了适合海洋作业的小型化、模块化、高效化精细控压装备及配套工艺,尤其在RCD系统结构、精细控压节流管汇结构、自动节流管汇回压补偿工艺等方面作出较大的优化升级,目前海洋化的精细控压钻井技术在加大推广应用,成为解决裂缝性储层、浅部大井眼钻进中的喷漏难题的有效手段之一。现场应用表明,精细控压钻井技术不仅有利于保障钻完井井控安全、减少井下复杂,而且可以大幅度降低钻井作业成本,在高压、裂缝发育、易漏失的储层钻井中具有广泛的应用前景,有助于提高勘探开发效益。

银额盆地哈日凹陷异常高压储层测试压裂的探究与实践

银根-额济纳旗盆地哈日凹陷多口探井已获得工业油气流,但该凹陷油气地质条件极为复杂,钻遇的储层埋藏深、岩性复杂,主要表现为地层压力高、岩性致密、抗压强度高。同时该区域处于勘探初期,同等埋深储层无可借鉴的邻井压裂资料,严重制约后续压裂工艺及勘探工作的开展。为此,提出了测试压裂的概念,通过对YH6井实施测试压裂压降数据的分析,求取储层的闭合压力、闭合时间、地应力、地层孔隙压力等参数,为主压裂的方案设计和优化,提供技术支撑基础,保证主压裂的成功实施。本研究对银额盆地高压、高应力储层的压裂试油作业和后续深层油气的勘探开发具有重大意义。

岩矿扫描录井在碳酸盐岩储层异常高压预测中的应用

做好碳酸盐岩储层异常高压随钻预测,是降低溢流、井漏风险发生概率的关键。针对塔里木盆地富满地区一间房-鹰山组碳酸盐岩储层异常高压预测难题,通过岩矿扫描录井技术,获取与断控缝洞型碳酸盐岩储层异常高压相关的孔隙度、裂缝数两个参数,引入反映裂缝复杂程度的裂缝复杂指数,并建立孔隙度与裂缝复杂指数图板,对塔里木盆地富满地区一间房-鹰山组碳酸盐岩储层异常高压进行识别和预测。以塔里木盆地富满地区FD 1井为例,应用孔隙度与裂缝复杂指数图板能有效表征碳酸盐岩储层异常高压段,为该地区碳酸盐岩储层异常高压研究和预测提供了一个新方法,也为下一步勘探开发提前采取工程措施,降低溢流、井漏风险发生概率提供技术支撑。

Relationship between heterogeneity of source rocks and genetic mechanism of abnormally high pressure

Based on the micro-fluorescence observation of polished sections of source rocks,two types of micro-layers with different wetting properties formed in thermal evolution,i.e.,oil-wetting and water-wetting micro-layers,are distinguished.The wetting property is found closely related to the abundance of organic matter and its occurrences with inorganic minerals.The alternating distribution and intercrossing of two types of micro-layers formed many separated spaces with different wettabilities.The strong capillary forces in these separated spaces with different wettibilities obstruct the cross flows of pore fluids and result in nearly independent and closed fluid systems.As a consequence,these spatially superposed spaces in source rocks bear the overburden pressure and then abnormally high pressures have developed in the whole source rock unit.Therefore,the abundance and occurrences of organic matter are the main inner factors influencing the formation of abnormally high pressures,whereas the formation,distribution and development of micro-layers with different wettabilities during the evolution of source rock determine the intensity and spatial distribution of abnormally high pressures.

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.

浅析空压机高压缸振动异常波动原因

分析空压机组高压缸的运行情况,排查机组异常波动的原因,对各个因素逐一论证,确认引起高压缸振动异常波动的原因是段间冷却器的腐蚀物及涂抹的二硫化钼润滑脂被携带至叶轮而导致叶轮结垢。通过计算高压缸各段多变效率评判了出现异常波动之后机组的稳定性和可靠性,并对机组各段间冷却器进行改造,通过更换管板和管束材质后,机组运行工况大大改善,为装置长周期运行提供参考依据。

基于钻井机械比能的地层压力监测方法在探井工程的应用

高风险探井为降低复杂情况处理难度以及减少损失,通常采用常规钻具实现安全完钻后进行测井取资料。根据dc指数PreVue地层压力监测缺少随钻测井数据参考印证,难以满足实钻指导需求。为此提出采用基于钻井机械比能的地层压力监测方法,分析预测地层压力变化趋势,进行异常高压风险预警,指导钻井工程有效采取防范措施。该监测方法在北部湾探井应用成功钻前预测外的异常高压,对安全高效钻井提供更充分保障。

西湖凹陷古近系致密砂岩气“三元耦合控藏”特征

针对西湖凹陷古近系致密砂岩气成藏机制与成藏模式尚不明确等问题,综合分析了烃源岩的特征与生排烃期次,研究异常高压的成因与分布特点,以及大型储集体的展布与物性特征,建立了致密砂岩气的成藏模式。研究结果表明:烃源岩、异常高压和致密储层“三元耦合控藏”是西湖凹陷致密砂岩气藏成藏关键因素,其中古近系煤系烃源岩条件优越,生气高峰期与储层致密形成时间一致,生烃增压同时提供了富厚的物质基础;异常高压改善储层物性,同时利于致密砂岩气的长距离运移和聚集;大规模的砂岩储集体发育,致密砂岩气在异常高压作用下汇聚成藏。西湖凹陷致密砂岩气藏呈现出“自源侧向-垂向”的成藏模式,共发育“原生型”和“改造型”2类致密砂岩气藏,具有良好的勘探前景。

应力敏感特低渗气藏绝对无阻流量计算新方法

为准确评价特低渗气藏产能,推导考虑应力敏感效应的气井产能方程,建立了特低渗气藏绝对无阻流量计算新方法。通过产能方程左端项数值与产气量的线性关系,确定方程系数A和B,建立考虑应力敏感效应的气井产能方程和绝对无阻流量计算公式,提高特低渗气藏产能预测精度。经S气藏A1、B1、B2井现场应用,相比于忽略应力敏感影响,应力敏感的气井绝对无阻流量下降19%,设计产能精度达到90.4%和95.0%,表明应力敏感效应对气井产能影响较大。新方法更适用于特低渗气藏的产能评价,具有较大的推广应用价值。

地层压力监测过程中向下预测实时地层压力技术的开发与应用

地层压力的准确监测在窄窗口钻井作业中非常重要。钻井作业前,需要先确定安全密度窗口。地层压力和地质结构复杂,钻前的地层压力预测与监测的地层压力有一定偏差,在实钻过程中会遇到实际地层压力高或低于钻前模型预测,如果处理不当,会引起溢流或漏失等问题。为此介绍一种新的实时预测地层压力的技术,通过拟合钻前模型与监测结果校正地层测试压力数据,提高钻前模型的精确度,并用于待钻井段。该技术在现场施工中取得了较好的应用效果,可为今后实时预测地层压力提供借鉴。

核电厂高加水位异常分析及应对措施

秦山地区近年来发生多起高加疏水故障引起的降功率或功率波动事件,高压加热器的正常、稳定运行对机组的安全和效率有重要影响。本文对秦山第二核电厂60万千瓦级压水堆机组高压加热器近年来运行中的水位异常现象进行分析总结,提出相应的应对措施,以减少高加水位异常事件的发生,并在瞬态发生时以便运行人员能够及时、准确干预,防止事故扩大化。

热动力站蒸汽管道热膨胀异常原因分析及改进措施

热动力站蒸汽管道由热膨胀引发的安全运行隐患将直接影响工厂的安全生产。针对热动力站易出现的管道、支吊架变形、过载热位移过大等异常问题,通过定量分析设计、安装及运行过程,评判造成管道热膨胀异常的关键因素,结果表明蒸汽母管刚性支吊架设计不合理、部分管系柔性偏大、安装过程支吊架性能降低或失效、运行过程缺乏有效处理措施是主要原因,采取优化支吊架、管道布置,达到管道系统“刚柔并济”,可有效消除热膨胀异常引起的安全隐患。经应力模拟计算,热动力站蒸汽管道系统热应力、热位移及设备推力显著降低,系统最大热应力由238.3 MPa降至176.23 MPa,原两处最大位位移量分别减少至17 mm和56 mm,对设备推力及力矩最高分别为10016.37 N和33032.37 N·m,最高降幅93.59%,提高了蒸汽管道系统稳定、安全及连续运行水平。研究结论可为高温高压蒸汽管道的设计、安装及运行提供一定的技术借鉴。

华北东濮凹陷异常高压与流体活动及其对储集砂岩成岩作用的制约

Basin-Mod软件模拟显示东濮凹陷35Ma左右孔隙流体已出现较高异常压力,综合分析表明欠压实作用是发育异常高压的主要机制。处于异常高压带内的泥岩存在微裂隙带,是异常高压流体压裂的直接结果井可以成为流体运移的通道。通过典型研究区砂岩压实(溶)量、压实-胶结关系、沉积参数-储集物性的对比,表明异常高压流体的确对砂岩的压实作用具有抑制作用。另一方面,自生石英流体包体均一温度大部分在105～145℃之间,频数呈多峰式展布,可能显示幕式流体活动。该温度范围内由于没有有机酸的大规模生成,泥岩频繁发生的幕式流体泄压活动,使得富含CO_3^(2-)的高压流体在注入砂岩(低压区)孔隙后易与Ca^(2+)、Mg^(2+)、Fe^(2+)等离子结合,导致砂岩储层发生强烈的(晚期)碳酸盐沉淀和胶结作用。