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1.
钻井实践表明,钻井液侵入会改变井壁围岩特性,例如岩石强度、孔隙压力等。在非常规的含水合物地层,钻井液侵入还可能诱发地层中水合物分解和再形成,从而对井壁稳定和测井解释产生影响。因此,研究钻井液在含水合物地层中侵入流动特性有非常重要的理论和实际应用价值。基于野外水合物储层的相关数据和室内实验模拟系统,采用数值模拟方法研究了实验尺度下钻井液在含水合物地层中的侵入流动规律及其对储层物性的影响。模拟结果可为后续实验模拟方案设计以及热开采研究提供一定的指导作用。 相似文献
2.
Focused fluid flow in the Baiyun Sag, northern South China Sea: implications for the source of gas in hydrate reservoirs 总被引：1，自引：0，他引：1
The origin and migration of natural gas and the accumulation of gas hydrates within the Pearl River Mouth Basin of the northern South China Sea are poorly understood. Based on high-resolution 2D/3D seismic data, three environments of focused fluid flow: gas chimneys, mud diapirs and active faults have been identified. Widespread gas chimneys that act as important conduits for fluid flow are located below bottom simulating reflections and above basal uplifts. The occurrence and evolution of gas chimneys can be divided into a violent eruptive stage and a quiet seepage stage. For most gas chimneys, the strong eruptions are deduced to have happened during the Dongsha Movement in the latest Miocene, which are observed below Pliocene strata and few active faults develop above the top of the Miocene. The formation pressures of the Baiyun Sag currently are considered to be normal, based on these terms: 1) Borehole pressure tests with pressure coefficients of 1.043–1.047; 2) The distribution of gas chimneys is limited to strata older than the Pliocene; 3) Disseminated methane hydrates, rather than fractured hydrates, are found in the hydrate samples; 4) The gas hydrate is mainly charged with biogenic gas rather than thermogenic gas based on the chemical tests from gas hydrates cores. However, periods of quiet focused fluid flow also enable the establishment of good conduits for the migration of abundant biogenic gas and lesser volumes of thermogenic gas. A geological model governing fluid flow has been proposed to interpret the release of overpressure, the migration of fluids and the formation of gas hydrates, in an integrated manner. This model suggests that gas chimneys positioned above basal uplifts were caused by the Dongsha Movement at about 5.5 Ma. Biogenic gas occupies the strata above the base of the middle Miocene and migrates slowly into the gas chimney columns. Some of the biogenic gas and small volumes of thermogenic gas eventually contribute to the formation of the gas hydrates. 相似文献
3.
海底泥底辟(泥火山)与周缘发育的天然气水合物存在着密切的关联,表现在静态要素和动态成藏2个方面。作为一种重要而有效的运移通道类型,泥底辟(泥火山)携带的气体将是天然气水合物的重要气体来源。同时,含气流体沿着泥底辟(泥火山)的上侵,可能会导致上覆地层中温压场和地球化学组分的改变,进而引起天然气水合物稳定带厚度的变化。因此,泥底辟(泥火山)将控制天然气水合物的成藏,如位于构造中心部位的矿物低温热液成藏模式和位于构造边缘的矿物交代成藏模式。另一方面,泥底辟(泥火山)的不同演化阶段将对天然气水合物的形成和富集产生不同的影响。早期阶段,泥底辟(泥火山)形成的运移通道可能并未延伸到天然气水合物稳定带,导致气源供给不够充分;中期阶段,天然气水合物成藏条件匹配良好,利于天然气水合物的生成;晚期阶段,泥火山喷发带来的高热量含气流体引起天然气水合物稳定带的热异常,可能导致天然气水合物的分解,直至泥火山活动平静期,天然气水合物再次成藏。 相似文献
4.
Submarine landslides have been observed in the Baiyun Depression of the South China Sea. The occurrence of hydrates below these landslides indicates that these slope instabilities may be closely related to the massive release of methane. In this study, we used a simple Monte-Carlo model to determine the first-order deformation pattern of a gravitationally destabilizing slope. The results show that a stress concentration occurs due to hydrate dissociation on the nearby glide surface and on top of a gas chimney structure. Upon the dissolution of the gas hydrate, slope failure occurs due to the excess pore pressure generated by the dissociation of the gas hydrates. When gas hydrates dissociate at shallow depths, the excess pore pressure generated can be greater than the total stress acting at those points, along with the forces that resist sliding. Initially, the failure occurs at the toe of the slope, then extends to the interior. Although our investigation focused only on the contribution of hydrate decomposition to submarine landslide, this process is also affected by both the slope material properties and topography. 相似文献
5.
Simulating the effect of hydrate dissociation on wellhead stability during oil and gas development in deepwater 总被引：1，自引：0，他引：1
It is well known that methane hydrate has been identified as an alternative resource due to its massive reserves and clean property. However, hydrate dissociation during oil and gas development (OGD) process in deep water can affect the stability of subsea equipment and formation. Currently, there is a serious lack of studies over quantitative assessment on the effects of hydrate dissociation on wellhead stability. In order to solve this problem, ABAQUS finite element software was used to develop a model and to evaluate the behavior of wellhead caused by hydrate dissociation. The factors that affect the wellhead stability include dissociation range, depth of hydrate formation and mechanical properties of dissociated hydrate region. Based on these, series of simulations were carried out to determine the wellhead displacement. The results revealed that, continuous dissociation of hydrate in homogeneous and isotropic formations can causes the non-linear increment in vertical displacement of wellhead. The displacement of wellhead showed good agreement with the settlement of overlying formations under the same conditions. In addition, the shallower and thicker hydrate formation can aggravate the influence of hydrate dissociation on the wellhead stability. Further, it was observed that with the declining elastic modulus and Poisson’s ratio, the wellhead displacement increases. Hence, these findings not only confirm the effect of hydrate dissociation on the wellhead stability, but also lend support to the actions, such as cooling the drilling fluid, which can reduce the hydrate dissociation range and further make deepwater operations safer and more efficient. 相似文献
6.
利用微生物诱导碳酸钙沉积（MICP）技术来提高油气井固井二界面胶结质量近年来受到了越来越多的重视。当前,针对3 000 m以浅油气井已实现了含成矿微生物的固井水泥浆技术。为了使固井水泥浆滤液中的成矿微生物在二界面处高效发挥MICP作用以提高二界面胶结质量,还需在钻井过程中利用钻井液携带CaCl2的渗透向井周地层中预先注入一定量的钙源。因此,有必要研究含CaCl2钻井液在井周地层的渗透规律,从而合理控制CaCl2的注入量和钻井成本。基于此,以当前常用的环保水基聚合物钻井液为基本载体,综合考虑钻井液渗透时在井壁处泥饼动态形成机理、井周地层物性参数变化规律以及含CaCl2水基聚合物钻井液流变性等因素,利用理论计算与模拟实验相结合的方法,建立了含CaCl2水基聚合物钻井液滤液沿井周地层渗透量及渗透距离的定量预测模型。该预测模型的计算结果与模拟实验测试结果吻合程度较高,证实该预测模型具有较好的可靠性,有助于为钻井生产企业合理优化钻井液和固井水泥浆施工工艺提供理论支持。 相似文献
7.
Various geological processes and features that might inflict hazards identified in the South China Sea by using new technologies and methods.These features include submarine landslides,pockmark fields,shallow free gas,gas hydrates,mud diapirs and earthquake tsunami,which are widely distributed in the continental slope and reefal islands of the South China Sea.Although the study and assessment of geohazards in the South China Sea came into operation only recently,advances in various aspects are evolving at full speed to comply with National Marine Strategy and‘the Belt and Road’Policy.The characteristics of geohazards in deep-water seafloor of the South China Sea are summarized based on new scientific advances.This progress is aimed to aid ongoing deep-water drilling activities and decrease geological risks in ocean development. 相似文献
8.
Gas hydrates-the firm crystal connections formed water (water, ice, water vapor) and low-molecular waterproof natural gases (mainly methane) whose crystal structure effectively compresses gas: each cubic meter of hydrate can yield over 160 m3 of methane.In present time exploitation of the Messoyahsk (Russia) and Mallik (Canada) deposits of gas hydrates in is conducted actively. The further perfection of prospecting methods in the field of studying gas hydrates containing sediments in round extent depends on improvement of geophysical and well test research, among which native-state core drilling is one of the major. Sampling native-state core from gas hydrates sediments keeping not only original composition, but structural-textural features of their construction.Despite of appeal of use gas hydrates as the perspective and ecologically pure fuel possessing huge resources, investigation and development of their deposits can lead to a number of the negative consequences connected with arising hazards for maintenance of their technical and ecological safety of carrying out. Scales of arising problems can change from local up to regional and even global. 相似文献
9.
V.K. Chistyakov Youhong SUN Chen CHEN Zupei ZHANG 《东北亚地学研究》2006,9(2):164-167
Gas hydrates-the firm crystal connections formed water （water, ice, water vapor） and low-molecu- lar waterproof natural gases （mainly methane） whose crystal structure effectively compresses gas： each cubic meter of hydrate can yield over 160 m^3 of methane. In present time exploitation of the Messoyahsk （Russia） and Mallik （Canada） deposits of gas hydrates in is conducted actively. The further perfection of prospecting methods in the field of studying gas hydrates containing sediments in round extent depends on improvement of geophysical and well test research, among which native-state core drilling is one of the major. Sampling nativestate core from gas hydrates sediments keeping not only original composition, but structural-textural features of their construction. Despite of appeal of use gas hydrates as the perspective and ecologically pure fuel possessing huge resources, investigation and development of their deposits can lead to a number of the negative consequences connected with arising hazards for maintenance of their technical and ecological safety of carrying out. Scales of arising problems can change from local up to regional and even global. 相似文献
10.
天然气水合物开采井眼出砂问题是当前水合物产业化急需突破的瓶颈之一,解决水合物开采时防砂与产能平衡问题是实现水合物安全高效、长期可控开采的关键.我国海域典型水合物储层属于弱固结的低渗泥质粉砂储层,其面临的防砂控泥与增产矛盾较为突出.厘清不同水合物储层和开采条件下的井眼出砂规律并揭示其机理,进而制定科学合理的防砂控泥措施以实现产能最大化是解决上述矛盾的途径所在.从理论分析、数值模拟、室内实验和现场试采4个角度介绍了世界范围内已开展的水合物出砂防砂情况,分析总结了水合物储层出砂影响因素及出砂机理,最后探讨了目前出砂研究存在的问题和挑战,并给出了相应的建议,旨在为后续水合物开采井眼出砂预测和防控研究提供思路和参考. 相似文献
11.
Numerical simulation for accuracy of velocity analysis in small-scale high-resolution marine multichannel seismic technology 总被引：1，自引：0，他引：1
When used with large energy sparkers, marine multichannel small-scale high-resolution seismic detection technology has a high resolution, high-detection precision, a wide applicable range, and is very flexible. Positive results have been achieved in submarine geological research, particularly in the investigation of marine gas hydrates. However, the amount of traveltime difference information is reduced for the velocity analysis under conditions of a shorter spread length, thus leading to poorer focusing of the velocity spectrum energy group and a lower accuracy of the velocity analysis. It is thus currently debatable whether the velocity analysis accuracy of short-arrangement multichannel seismic detection technology is able to meet the requirements of practical application in natural gas hydrate exploration. Therefore, in this study the bottom boundary of gas hydrates (Bottom Simulating Reflector, BSR) is used to conduct numerical simulation to discuss the accuracy of the velocity analysis related to such technology. Results show that a higher dominant frequency and smaller sampling interval are not only able to improve the seismic resolution, but they also compensate for the defects of the short-arrangement, thereby improving the accuracy of the velocity analysis. In conclusion, the accuracy of the velocity analysis in this small-scale, high-resolution, multi-channel seismic detection technology meets the requirements of natural gas hydrate exploration. 相似文献
12.
Gas hydrate research has significant importance for securing world energy resources, and has the potential to produce considerable
economic benefits. Previous studies have shown that the South China Sea is an area that harbors gas hydrates. However, there
is a lack of systematic investigations and understanding on the distribution of gas hydrate throughout the region. In this
paper, we applied mineral resource quantitative assessment techniques to forecast and estimate the potential distribution
of gas hydrate resources in the northern South China Sea. However, current hydrate samples from the South China Sea are too
few to produce models of occurrences. Thus, according to similarity and contrast principles of mineral outputs, we can use
a similar hydrate-mining environment with sufficient gas hydrate data as a testing ground for modeling northern South China
Sea gas hydrate conditions. We selected the Gulf of Mexico, which has extensively studied gas hydrates, to develop predictive
models of gas hydrate distributions, and to test errors in the model. Then, we compared the existing northern South China
Sea hydrate-mining data with the Gulf of Mexico characteristics, and collated the relevant data into the model. Subsequently,
we applied the model to the northern South China Sea to obtain the potential gas hydrate distribution of the area, and to
identify significant exploration targets. Finally, we evaluated the reliability of the predicted results. The south seabed
area of Taiwan Bank is recommended as a priority exploration target. The Zhujiang Mouth, Southeast Hainan, and Southwest Taiwan
Basins, including the South Bijia Basin, also are recommended as exploration target areas. In addition, the method in this
paper can provide a useful predictive approach for gas hydrate resource assessment, which gives a scientific basis for construction
and implementation of long-term planning for gas hydrate exploration and general exploitation of the seabed of China. 相似文献
13.
Weiwei Wang Dawei Wang Shiguo Wu David Völker Hongliu Zeng Guanqiang Cai Qingping Li 《中国海洋大学学报(英文版)》2018,17(1):83-100
Recent and paleo-submarine landslides are widely distributed within strata in deep-water areas along continental slopes, uplifts, and carbonate platforms on the north continental margin of the South China Sea (SCS). In this paper, high-resolution 3D seismic data and multibeam data based on seismic sedimentology and geomorphology are employed to assist in identifying submarine landslides. In addition, deposition models are proposed that are based on specific geological structures and features, and which illustrate the local stress field over entire submarine landslides in deep-water areas of the SCS. The SCS is one of the largest fluvial sediment sinks in enclosed or semi-enclosed marginal seas worldwide. It therefore provides a set of preconditions for the formation of submarine landslides, including rapid sediment accumulation, formation of gas hydrates, and fluid overpressure. A new concept involving temporal and spatial analyses is tested to construct a relationship between submarine landslides and different time scale trigger mechanisms, and three mechanisms are discussed in the context of spatial scale and temporal frequency: evolution of slope gradient and overpressure, global environmental changes, and tectonic events. Submarine landslides that are triggered by tectonic events are the largest but occur less frequently, while submarine landslides triggered by the combination of slope gradient and over-pressure evolution are the smallest but most frequently occurring events. In summary, analysis shows that the formation of submarine landslides is a complex process involving the operation of different factors on various time scales. 相似文献
14.
Estimation of S-wave velocity using logging data has mainly been performed for sandstone,mudstone and oil and gas strata,while its application to hydrate reservoirs has been largely overlooked.In this paper we present petrophysical methods to estimate the S-wave velocity of hydrate reservoirs with the P-wave velocity and the density as constraints.The three models used in this paper are an equivalent model(MBGL),a three-phase model(TPBE),and a thermo-elasticity model(TEM).The MBGL model can effectively describe the internal relationship among the components of the rock,and the estimated P-wave velocities are in good agreement with the measured data(2.8% error).However,in the TPBE model,the solid,liquid and gas phases are considered to be independent of each other,and the estimation results are relatively low(46.6% error).The TEM model is based on the sensitivity of the gas hydrate to temperature and pressure,and the accuracy of the estimation results is also high(3.6% error).Before the estimation,the occurrence patterns of hydrates in the Shenhu area were examined,and occurrence state one(the hydrate is in solid form in the reservoir) was selected for analysis.By using the known P-wave velocity and density as constraints,a reasonable S-wave velocity value(ranging from 400 to 1100 m s~(-1) and for a hydrate layer of 1100 m s~(-1)) can be obtained through multiple iterations.These methods and results provide new data and technical support for further research on hydrates and other geological features in the Shenhu area. 相似文献
15.
Natural gas hydrates are considered as strategic resources with commercial potential in the 21st century. Obvious BSR characteristics
will be shown on seismic profiles, if there exist natural gas hydrates. The AVO method is one of the methods which can be
used to identify and forecast lithologic characteristics and fluid properties by using the relationship between Amplitude
and Offset. AVO anomaly is one of the significant signs to check out whether or not there is free gas below the BSR, so it
can be used to detect natural gas hydrates from the seismic profile. Considering the geological and geophysical characteristics
of the Okinawa Trough and making use of the techniques mentioned above, we can conclude that the conditions there are favorable
for the formation and concentration of natural gas hydrates. By analyzing the data collected from the study area, one can
discover many different anomalous phenomena on the seismic profile which are related to the existence of natural gas hydrates.
Preliminary estimation of the natural gas hydrates in the Okinawa Trough shows that the trough is rich in natural gas hydrates
and may become a potential important resources exploration area. 相似文献
16.
Using a bottom simulating reflector(BSR) on a seismic profile to identify marine gas hydrate is a traditional seismic exploration method. However, owing to the abundance differences between the gas hydrate and free gas in different regions, the BSR may be unremarkable on the seismic profile and invisible in certain cases. With the improvement of exploration precision, difficulty arises in meeting the requirements of distinguishing the abundance differences in the gas hydrate based on BSR. Hence, we studied other sensitive attributes to ascertain the existence of gas hydrate and its abundance variations, eventually improving the success rate of drilling and productivity. In this paper, we analyzed the contradiction between the seismic profile data and drilling sampling data from the Blake Ridge. We extracted different attributes and performed multi-parameter constraint analysis based on the prestack elastic wave impedance inversion. Then, we compared the analysis results with the drilling sampling data. Eventually, we determined five sensitive attributes that can better indicate the existence of gas hydrate and its abundance variations. This method overcomes the limitations of recognizing the gas hydrate methods based on BSR or single inversion attribute. Moreover, the conclusions can notably improve the identification accuracy of marine gas hydrate and provide excellent reference significance for the recognition of marine gas hydrate. Notably, the different geological features of reservoirs feature different sensitivities to the prestacking attributes when using the prestack elastic inversion in different areas. 相似文献
17.
ZHAN Jiajia XU Huiwen CAI Hongliang .College of Construction Engineering Jilin University Changchun China .China Water Northeastern Investigation Design Research Co.Ltd Changchun China 《东北亚地学研究》2009,12(1):32-35
Drilling fluid additives has a major impact on rheology behavior and other performances of the drilling fluid. The key to low temperature drilling fluids is choosing antifreeze and polymer agent which have a strong ability in resisting low temperature. On the basis of determining glycol as antifreeze agent, the low-temperatureperformance and capacities of anti-collapse of regular validity mud agents have been studied, the mechanism of anti-caving of the partially hydrolyzed polyacrylamide （PHPA）, polypropylene potassium （KPA） and PAC-141 polymer additives have been also analyzed. A pilot study of compatibility between ethylene glycol and the polymers has educed that the polymers, ethylene glycol and inorganic salt are compatible, and they can significantly reduce the freezing point of drilling fluid. Anti-collapse ability of the drilling mud is the results of synergistic action among the agents. 相似文献
18.
为应对金刚石绳索取心钻进普遍发生的垮塌、造浆、钻杆内壁结泥皮等问题，完成了基于聚乙烯醇(PVA)为抑制剂的无固相防塌钻井液室内研究。通过泥页岩滚动回收试验、膨润土临界加量试验、泥球浸泡试验以及电动电位测试等对比了常用抑制剂的抑制效果；通过配伍性试验确定了增黏剂及降失水剂的种类和加量；对比了不同种类的污染物对所获配方钻井液综合性能的影响。结果表明，相比于NaCl、KCl等常规无机盐抑制剂，聚乙烯醇具有较强的抑制性，且抑制性与聚合度呈正相关；黄原胶(XC)、磺化褐煤树脂(SPNH)、磺化沥青(FT-1)可用作配制该钻井液的增黏提切剂和降失水剂；该配方钻井液可抗35% NaCl、4% CaCl2以及12%钙土的污染，能满足110℃温度范围内的使用要求，可在3 000 m深度范围内的强造浆地层、破碎地层、盐膏层等复杂地层中使用。 相似文献
19.
Drilling fluid additives has a major impact on rheology behavior and other performances of the drilling fluid. The key to low temperature drilling fluids is choosing antifreeze and polymer agent which have a strong ability in resisting low temperature. On the basis of determining glycol as antifreeze agent, the low-temperature-performance and capacities of anti-collapse of regular validity mud agents have been studied, the mechanism of anti-caving of the partially hydrolyzed polyacrylamide (PHPA), polypropylene potassium (KPA) and PAC-141 polymer additives have been also analyzed. A pilot study of compatibility between ethylene glycol and the polymers has educed that the polymers, ethylene glycol and inorganic salt are compatible, and they can significantly reduce the freezing point of drilling fluid. Anti-collapse ability of the drilling mud is the results of synergistic action among the agents. 相似文献
20.
Jin Jiapeng Wang Xiujuan He Min Li Jie Yan Chengzhi Li Yuanping Zhou Jilin Qian Jin 《中国海洋湖沼学报》2020,38(4):1188-1200
New acquired and reprocessed three-dimensional(3 D) seismic data were used to delineate the distribution and characterization of bottom simulating reflections(B SRs) in the Chaoshan Sag,in the eastern part of Dongsha Island,South China Sea.Three submarine canyons with different scales were interpreted from the 3 D seismic data,displaying three stages of canyon development and are related with the variation of BSR.Abundant faults were identified from the coherence and ant-tracing attributions extracted from3 D seismic data,which provide the evidence for fluid migration from deeper sediments to the gas hydrate stability zone(GHSZ).The uplift of Dongsha Island created a large number of faults and leads to the increased seafloor erosion.The erosion caused the cooling of the seafloor sediments and deepening of the base of the gas hydrate stability zone,which is attributed to the presence of paleo-BSR and BSR downward shift in the study area.Hence,methane gas may be released during the BSR resetting and gas hydrate dissociation related with seafloor ero sion. 相似文献