Capture the variation of the pore pressure with different geological age from seismic inversion study in the Jaisalmer sub-basin,India

Geoscientific evidence shows that various parameters such as compaction,buoyancy effect,hydrocarbon maturation,gas effect and tectonic activities control the pore pressure of sub-surface geology.Spatially controlled geoscientific data in the tectonically active areas is significantly useful for robust estimation of pre-drill pore pressure.The reservoir which is tectonically complex and pore pressure is changing frequently that circumference motivated us to conduct this study.The changes in pore pressure have been captured from the fine-scale to the broad scale in the Jaisalmer sub-basin.Pore pressure variation has been distinctly observed in pre-and post-Jurassic age based on the current study.Post-stack seismic inversion study was conducted to capturing the variation of pore pressure.Analysis of low-frequency spectrum and integrated interval velocity model provided a detailed feature of pore pressure in each compartment of the study area.Pore pressure estimated from well log data was correlated with seismic inversion based result.Based on the current study one well has been proposed where pore pressure was estimated and two distinguished trends are identified in the study zone.The approaches of the current study were analysed thoroughly and it will be highly useful in complex reservoir condition where pore pressure varies frequently.

High-pressure effect on inverse spinel LiCuVO_4:X-ray diffraction and Raman scattering

The effect of external quasi-hydrostatic pressure on the inverse spinel structure of LiCuVO4 was studied in this paper. High-pressure synchrotron X-ray diffraction and Raman spectroscopy measurements were carried out at room temperature up to 35.7 and 40.3 GPa, respectively. At a pressure of about 20 GPa, both Raman spectra and X-ray diffraction results indicate that LiCuVO4 was transformed into a monoclinic phase, which remained stable up to at least 35.7 GPa. Upon release of pressure, the high-pressure phase returned to the initial phase. The pressure dependence of the volume of low pressure orthorhombic phase and high-pressure monoclinic phase were described by a second-order Birch-Murnaghan equation of state, which yielded bulk modulus values of B0 = 197 （5） and 232（8） GPa, respectively. The results support the empirical suggestion that the oxide spinels have similar bulk modulus around 200 GPa.

Research on Multi-Wave Pore Pressure Prediction Method Based on Three Field Velocity Fusion

The optimization of velocity field is the core issue in reservoir seismic pressure prediction. For a long time, the seismic processing velocity analysis method has been used in the establishment of pressure prediction velocity field, which has a long research period and low resolution and restricts the accuracy of seismic pressure prediction;This paper proposed for the first time the use of machine learning algorithms, based on the feasibility analysis of wellbore logging pressure prediction, to integrate the CVI velocity inversion field, velocity sensitive post stack attribute field, and AVO P-wave and S-wave velocity reflectivity to obtain high-precision seismic P and S wave velocities. On this basis, high-resolution formation pore pressure and other parameters prediction based on multi waves is carried out. The pressure prediction accuracy is improved by more than 50% compared to the P-wave resolution of pore pressure prediction using only root mean square velocity. Practice has proven that the research method has certain reference significance for reservoir pore pressure prediction.

Determination of interfacial heat transfer coefficient and its application in high pressure die casting process

In this paper,the research progress of the interfacial heat transfer in high pressure die casting(HPDC)is reviewed.Results including determination of the interfacial heat transfer coefficient(IHTC),influence of casting thickness,process parameters and casting alloys on the IHTC are summarized and discussed.A thermal boundary condition model was developed based on the two correlations:(a)IHTC and casting solid fraction and(b)IHTC peak value and initial die surface temperature.The boundary model was then applied during the determination of the temperature field in HPDC and excellent agreement was found.

Multi-exponential model to describe pressure-dependent P-and S-wave velocities and its use to estimate the crack aspect ratio

We present new quantitative model describing the pressure dependence of acoustic P-and S-wave velocities.Assuming that a variety of individual mechanisms or defects(such as cracks,pore collapse and grain crushing)can contribute to the pressure-dependent change of the wave velocity,we order a characteristic pressure to all of them and allow a series of exponential terms in the description of the(Pand S-waves)velocity-pressure function.We estimate the parameters of the multi-exponential rock physical model in inversion procedures using laboratory measured P-and S-wave velocity data.As is known,the conventional damped least squares method gives acceptable results only when one or two individual mechanisms are assumed.Increasing the number of exponential terms leads to highly nonlinear ill-posed inverse problem.Due to this reason,we develop the spectral inversion method(SIM)in which the velocity amplitudes(the spectral lines in the characteristic pressure spectrum)are only considered as unknowns.The characteristic pressures(belonging to the velocity amplitudes)are excluded from the set of inversion unknowns,instead,they are defined in a set of fixed positions equidistantly distributed in the actual interval of the independent variable(pressure).Through this novel linear inversion method,we estimate the parameters of the multi-exponential rock physical model using laboratory measured P-and S-wave velocity data.The characteristic pressures are related to the closing pressures of cracks which are described by well-known rock mechanical relationships depending on the aspect ratio of elliptical cracks.This gives the possibility to estimate the aspect ratios in terms of the characteristic pressures.

Moment tensor inversion of focal mechanism for the aftershock sequence of 1982 Lulong M_S =6.1 earthquake

Using the moment tensor inversion method, we calculate the focal mechanisms of the aftershock sequence of the Ms=6.1 Lulong earthquake occurred on October 19, 1982 in Hebei Province. We found that the pressure axis in Lulong basin is nearly in the east-west direction with an azimuth of N74°E. However, in the north of the basin the stress axis changes to N43°E; and in some places near the center of the basin it changes to the northwest that is almost perpendicular to the P axis obtained by us from those events around the basin. This feature illuminates that in Lulong earthquake sequence, the stress direction is different in different parts of crustal structure, which shows that the tectonic movement in Lulong region is complex. This is because that Lulong is located in the eastern part of Chinese mainland and is subject to the compression of Japanese Sea Basin driven by the Pacific Plate. On the other hand, nipped by the Yanshan and North China blocks, Lulong is obviously restricted by the block boundaries.

Coupled Inversion of Pressure and Tiltmeter Data for Mapping Hydraulic Fracture Geometry

Pressure and tilt data are jointly inverted to simultaneously map the orientation and dimensions of a hydraulic fracture.The deformation induced by a fracture under internal pressure is modeled using the distributed dislocation technique.The planar fracture is represented by four quarter ellipses,joined at the center and sharing semi-axes.This configuration provides a straightforward model for characterizing asymmetric fracture geometry.The inverse problem of mapping the fracture geometry is formulated using the Bayesian probabilistic method,combining the a priori information on the fracture model with updated information from pressure and tilt data.Solving the nonlinear inverse problem is achieved by pseudo-randomly sampling the posterior probability distribution through the Markov chain Monte Carlo method.The resulting posterior probability distribution is then explored to assess uncertainty,resolution,and correlation between model parameters.Numerical experiments are conducted to verify the accuracy and validity of the proposed analysis method in mapping the fracture geometry using synthetic pressure and tilt data.

Simultaneous inversion of permeability,skin and boundary from pressure transient test data in three-dimensional single well reservoir model

This study presents a novel approach for simultaneous inversion of the key reservoir parameters like horizontal permeability,vertical permeability,skin,and boundary distances for spatial distribution across the grid cells in a 3D single well reservoir model(SWRM).These parameters are first estimated from the standard pressure transient analysis of well test pressure and rate data,which also act as a priori for the inverse problem.A field-worthy layer cake geological model is prepared based on the prior information obtained from pressure transient analysis,followed by a sequential flow simulation of field well test operation.The simulation results provide the model pressure versus rate data as the synthetic data for this study.A cost function is defined incorporating the well test pressure data and model pressure data,which would determine the convergence.The inversion process is to optimize the spatial distribution of reservoir parameters to minimize the difference between the measured pressure transient data and the modelled one,which is obtained from the multiphase fluid flow simulator that solves the implicit black-oil fluid-flow diffusivity equations at every step.A Gauss-Newton(GN)inversion scheme is used for the inversion.The reliability of inversion results depends on the accuracy of priori reservoir parameters fed to the solver,which can be refined if required through uncertainty parameter optimization(UPO).This approach helps to obtain a faster and reliable update of reservoir parameters in a layer cake homogeneous geomodel,hereby introducing the required heterogeneity.This increases the confidence and reliability of a geomodel,which is further used for various production prediction strategies.

Practice and Cognition of Midway VSP in High Temperature and High Pressure Field of South China Sea

Ying-Qiong Basin is a typical high-temperature and overpressure basin, which is the main battlefield of oil and gas exploration in South China Sea and has made great breakthroughs in recent years. During drilling process in high pressure, the relationship between the deep and the pressure is directly related to the drilling safety and costs. In order to improve prediction accuracy, the VSP operation is carried out through the midway, and three points have been obtained: 1) The VSP has a higher accuracy of the interface depth in certain depth range of the drill bit. 2) When the low-frequency trend prediction is accurate before the drill bit, interval velocity of the VSP inversion is consistent with the formation velocity. 3) The VSP pressure forecast is based on the inversion layer velocity and under-compaction pressure. If the velocity prediction is not accurate, the pressure forecast must be erroneous. If the pressure has other sources, the formation pressure is not accurate even if the inversion velocity is accurate. The application scope and exploration effect of midway VSP operation are summarized and applied to Ledong 10-1 block in Yinggehai basin, which realize the breakthrough in the field of high temperature overpressure and provide the basis for other similar exploration areas to do VSP operation.

The Application of Pressure Coefficient in Judging Normal Pressure Reservoirs Connectivity—A Case Study of LD21-X and KL3-Xoilfield in Bohai Bay

Reservoir connectivity is a critical issue in the process of oil-gas exploration and development. According to the theory of fluid mechanics and the achievements of many scholars, a connected reservoir coincides with a unified formation pressure system;there is a linear relationship between formation pressure and depth in normal pressure system reservoir. However, in high-permeability or multi-phase fluid reservoirs, this method has poor applicability and limitations. Through theoretical analysis and formula derivation, a new method for judging the connectivity of normal pressure reservoirs is found, that is, the inverse proportional function relationship between the pressure coefficient and the depth. In this paper, the relationship between the pressure system and the inverse proportional function has been verified. The function of the same pressure system is unique, monotonic, and has unified asymptote and symmetry axis and vice versa. Examples show that the inverse proportional function is more accurate and reliable for judging reservoir connectivity than the linear function.

Research on Pore Pressure-Depth Characteristics in Normal Pressure Reservoir, Bohai Sea Oilfield

In normal pressure of reservoir, formation pressure and depth can not fully reflect the linear relationship between the formation pressure with depth, the change rule of reservoir measured formation pressure and often reduced pressure, understanding unclear cause fluid properties. By introducing basic principles of hydrostatics. The relationship between pressure coefficient and mathematical depth is discussed by mathematical induction analysis of measured pressure data of nearly 50 normal pressure reservoirs in Bohai Oilfield. The results show that the reservoir pressure data is linearly distributed with depth, and the pressure coefficient is inversely proportional to depth. When the depth becomes shallower, the pressure coefficient increases and approaches the reservoir level. As the depth increases, the pressure coefficient decreases and approaches the hydrostatic pressure coefficient infinitely. The study can more accurately analyze the reservoir pressure changes, which is helpful to study the oil and water distribution, reservoir connectivity and fluid properties of atmospheric pressure reservoirs.

An efficient probabilistic design approach for tunnel face stability by inverse reliability analysis

In order to maintain the safety of underground constructions that significantly involve geo-material uncertainties,this paper delivers a new computation framework for conducting reliability-based design(RBD)of shallow tunnel face stability,utilizing a simplified inverse first-order reliability method(FORM).The limit state functions defining tunnel face stability are established for both collapse and blow-out modes of the tunnel face failure,respectively,and the deterministic results of the tunnel face support pressure are obtained through three-dimensional finite element limit analysis(FELA).Because the inverse reliability method can directly capture the design support pressure according to prescribed target reliability index,the computational cost for probabilistic design of tunnel face stability is greatly reduced.By comparison with Monte Carlo simulation results,the accuracy and feasibility of the proposed method are verified.Further,this study presents a series of reliability-based design charts for vividly understanding the limit support pressure on tunnel face in both cohesionless(sandy)soil and cohesive soil stratums,and their optimal support pressure ranges are highlighted.The results show that in the case of sandy soil stratum,the blowout failure of tunnel face is extremely unlikely,whereas the collapse is the only possible failure mode.The parametric study of various geotechnical uncertainties also reveals that ignoring the potential correlation between soil shear strength parameters will lead to over-designed support pressure,and the coefficient of variation of internal friction angle has a greater influence on the tunnel face failure probability than that of the cohesion.

3D modeling of abnormal pore pressure in shallow offshore Niger delta: An application of seismic inversion

Pore pressure is the pressure associated with fluids in the pore spaces of sedimentary rocks. Thispressure varies from hydrostatic to severe overpressure. It is classified as abnormal pressure when itdeviates from hydrostatic pressure. Incorrect prediction or the absence of pore pressure evaluation canlead to severe damage of the drilling platform, loss of personnel, waste of resources and environmentalpollution. This study was carried out in an offshore field in Niger Delta with an objective of predicting theabnormal pressure regime from the seismic volume using seismic inversion technique. First, weemployed the Eaton’s and Bower’s model of predicting pore pressure from Well log. The predicted porepressure from the well was used to calibrate the P-impedance that was used in the inversion process. Apressure-based model for the seismic inversion process was developed. This was constrained by therelationship between the P-impedance and pore pressure in the study area. The predicted pore pressurefrom the Well logs aligned with the measured pore pressure in the formation. At about 3600 m to end ofthe Well, depicts a pressure regime that is a deviation from the hydrostatic pressure trend. The abnormalpressure regime is marked by the region where a change is observed in the normal compaction trendline. The cross plot of acoustic impedance against pore pressure reveals a linear relationship;with adirect relationship indicating a normal pressure interval and the indirect relationship at the abnormalpressure regime. The inverted 3D pressure result from the seismic volume validates the normalcompaction trend line and also the pressure values estimated from the Well logs. The abnormal pressureregime in the study area is predicted to be found towards the end of Agbada Formation and through theAkata Formation due to the un-compacted shales.

双封隔取样压力数据深入解释方法研究

双封隔器是一种地层测试测压取样工具,取样过程通常需要泵抽几小时甚至十几小时,取得地层流体样品,获得压力和流量数据,但无法真实反映地层渗透率的探测范围。利用油藏模拟软件模拟双封隔器泵抽取样过程,引入Schroeter算法和Levitan算法这两种压力/流量数据反褶积算法,反演渗透率参数波及半径从几厘米到上百米,并使用数值模拟案例验证了只利用取样完成后的压力恢复数据进行反褶积方法的准确性和合理性。该研究应用于双封隔现场测井数据,采用反褶积方法得到渗透率探测半径31m,反褶积处理后的数据可用于产能预测,对正确认识油气藏具有重要意义。

基于孔压静力触探试验测试数据的原位固结系数物理信息神经网络反演方法

固结系数是软基沉降计算和稳定性分析的关键参数,现有固结系数原位测试方法存在耗时长且精度低的缺点。根据孔压静力触探试验(piezoconepenetrationtest,简称CPTU)贯入机制与锥肩超孔隙水压力消散模式,采用圆孔扩张理论和轴对称固结方程描述CPTU锥肩超孔隙水压力的形成、发展和消散过程,利用神经网络自动微分功能将轴对称固结方程嵌入深度神经网络,通过物理方程损失函数、边界条件损失函数和初始条件损失函数形成神经网络的物理信息约束,同时将CPTU孔压测试数据作为数据驱动项,以最小化超孔隙水压力损失函数为优化目标,建立了CPTU孔压测试数据反演场地原位固结系数的物理信息神经网络(physics-informed neural networks,简称PINNs)模型。通过已有离心模型试验数据反演验证了PINNs模型反演场地原位固结系数的有效性,并利用CPTU孔压测试数据分析了PINNs模型反演原位固结系数的鲁棒性。结果表明:提出的PINNs模型能够有效利用CPTU孔压测试数据快速准确地反演场地原位固结系数;由于模型融入了物理机制约束,所需训练数据量少,且对有噪声的孔压测试数据具有较强的鲁棒性和泛化性能,为准确、快速可靠测试场地原位固结系数提供了有效途径。

助推器对巡飞弹气动特性和静稳定性的影响

针对助推分离舱外形对巡飞弹气动特性和静稳定性的影响,通过对船尾收缩比和分离舱外形设计的研究,分析了船尾收缩比和曲线过渡对改善气动特性和稳定性的机理,形成了“增大船尾收缩比-改善曲线过渡”的设计思想。结果表明:船尾收缩比是影响流动特性和气动特性的主要因素。增大船尾收缩比可以有效减小局部分离的面积,改善流动状况,改进后的零阻减小了1.5%~2%,静稳定度提高了1%~3%;在特定的船尾收缩比下,船尾与助推分离舱曲线过渡对阻力特性和静稳定性有一定改善效果。

基于孔压变化的瓦斯压力预判

为了缩短煤层瓦斯压力测压周期,提高瓦斯压力测量的精确度,对前人的主动式压力测定研究进行了总结和分析,提出了存在瓦斯压力预判研究不足的问题。针对该问题进行了瓦斯压力测定的模拟实验研究,研究发现压力测定过程分为孔压急速上升期、缓慢上升期、趋于稳定期与达到稳定期4个阶段,急速上升期孔压变化率远大于其他3个阶段。并构建了基于煤层瓦斯压力、模拟煤层孔隙大小、模拟钻孔内压力变化率3参数的瓦斯压力预判数学模型,使用该模型对煤层瓦斯压力进行了合理区间的验证,结果表明,与真实瓦斯压力相比存在较小误差,为主动式煤层瓦斯压力测定中补偿气体最佳注气压力的确定提供了理论依据。

基于深部煤体应力监测的采动应力集中区域范围分析研究

现阶段煤体应力监测位置单一且固定,导致煤体应力监测数据缺少多样性,为获得采动过程中煤体深部应力数据,得到采动影响下的深部煤体应力集中区域范围,以赵楼煤矿7303工作面为工程实验现场,通过在工作面两顺槽布置深部应力监测测点的方式获得采动影响下深部应力数据,同时通过深部应力监测钻孔应力计实验室安装性能试验、FLAC^(3D)数值模拟及现场被动CT反演对比分析,对煤体深部应力采动影响过程中的应力集中范围进行分析研究,得出以下结论:深部应力监测补偿系数K的取值规律为:20m监测时K取1.02,30m监测时K取1.03,50m监测时K取1.05,70m监测时K取1.07;通过数值模拟分析得出,以赵楼煤矿工作面岩石力学参数为基础,采动影响下深部煤体应力监测峰值位置在20~30m之间,且在25m左右达到峰值位置,且峰值应力约为23.6MPa,随着监测布置深度增大,垂直应力逐渐降低;通过被动CT反演数据,对比现场实测的深部应力监测数据分析,得出布置在20m深部应力监测范围内的测点,能更好地反映采动影响下煤体应力变化的结论。

石屏一矿掘进工作面煤层瓦斯参数反演模型研究及应用

为提升煤与瓦斯突出预测和防治的准确性、可靠性和效率,首先,基于煤层瓦斯赋存规律、吸附解吸特征及瓦斯运移规律相关理论构建掘进工作面瓦斯参数反演模型;其次,将瓦斯反演模型内嵌到煤与瓦斯突出实时监测预警系统软件中,对石屏一矿C19上煤层13019上机巷掘进工作面的瓦斯含量和瓦斯压力进行反演预测;最后,采用DGC瓦斯含量直接测定法实测现场数据对模型反演结果进行对比验证。反算数值与实测数值对比表明,煤体瓦斯含量和压力反演计算结果准确可靠。