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41.
储层压实作用和胶结作用的压力响应特征 总被引：1，自引：1，他引：0
为了在发育异常高压沉积盆地的中深层进行有效的油气勘探,综合运用薄片、岩心常规、粒度分析、SEM等分析化验资料,探讨了渤中凹陷西北次凹储层压实作用和胶结作用的压力响应特征。得到了异常高压对机械压实具有抑制作用的有力证据。证实了不同胶结物类型有不同的压力响应特征。研究认为,每超静水压力7 MPa的异常高压可保存约2.0%原生孔隙。胶结强度的压力响应特征呈斜坡状:1陡坡段,远离高压界面的常压带→高压界面外280 m,胶结强度迅速增强,以弱胶结为特征,胶结物以自生黏土矿物为主,约占总胶结物的85%;2缓坡段,高压界面外280 m→异常高压带,胶结强度缓慢增大,以强—中胶结为特征,胶结物以碳酸盐为主,约占总胶结物的75%以上。在高压界面附近的常压带,碳酸盐胶结作用的压力响应厚度比自生黏土矿物的响应厚度小,前者约280 m,后者430 m。研究区原生孔隙与渗透率具有较好相关性,相关系数可达0.77,表明原生孔隙发育的砂岩是优质储层。研究结果可为在异常高压发育的盆地中深层寻找优质储层提供理论依据。 相似文献
42.
The porosity and hence volume of argillaceous sediments is determined by: (1) the magnitude of the effective stress acting within the sediment; (2) the previous stress history of the sediment; and (3) at shallow depths of burial, by features such as the mineralogy and the nature of the depositional environment. Stress paths and the critical state diagrams for a number of clays are used to investigate the range of porosities possible in argillaceous sediments as the effective stresses increase. It is found that all porosity/effective stress curves converge at large stresses. The change in porosity is strongly dependent on the mean effective stress but largely independent of the deviatoric stress, and thus is largely independent of the nature of the stress field acting on the basin (compressional, extensional etc.). Because of the dependence of porosity on the mean effective stress, no simple relationship exists between porosity and depth of burial but in the absence of overpressured pore fluids and assuming the sediment is not overconsolidated, it is possible to contour the porosity/effective stress diagram in terms of burial depths. These data should assist in recalculating stratigraphic thicknesses for basin reconstruction and stratigraphic correlation studies. 相似文献
43.
Kolawole J. Osinubi Charles M. O. Nwaiwu 《Geotechnical and Geological Engineering》2008,26(5):603-611
Specimens prepared from three lateritic soil samples were subjected to drying under laboratory conditions. Volumetric shrinkage
strains were measured at the end of the drying period. Results of this study indicate that, for the lateritic soils tested,
volumetric shrinkage strains are influenced by soil composition and compaction conditions. Volumetric shrinkage strain increased
with higher compaction water content. The influence of compaction water content on measured volumetric shrinkage strain was
more pronounced in specimens with higher fines content. A regression equation was developed from the data to estimate volumetric
shrinkage strain given the compaction water content relative to optimum, plasticity index, fines content and compactive effort. 相似文献
44.
Deformation bands in porous sandstones have been extensively studied for four decades, whereas comparatively less is known about deformation bands in porous carbonate rocks, particularly in extensional settings. Here, we investigate porous grainstones of the Globigerina Limestone Formation in Malta, which contain several types of deformation bands in the hangingwall of the Maghlaq Fault: (i) bed-parallel pure compaction bands (PCB); (ii) pressure solution-dominated compactive shear bands (SCSB) and iii) cataclasis-dominated compactive shear bands (CCSB). Geometric and kinematic analyses show that the bands formed sequentially in the hangingwall of the evolving Maghlaq growth fault. PCBs formed first due to fault-controlled subsidence and vertical loading; a (semi-)tectonic control on PCB formation is thus documented for the first time in an extensional setting. Pressure solution (dominating SCSBs) and cataclasis (dominating CCSBs) appear to have operated separately, and not in concert. Our findings therefore suggest that, in some carbonate rocks, cataclasis within deformation bands may develop irrespective of whether pressure solution processes are involved. We suggest this may be related to stress state, and that whereas pressure solution is a significant facilitator of grain size reduction in contractional settings, grain size reduction within deformation bands in extensional settings is less dependent on pressure solution processes. 相似文献
45.
Mechanical compaction in heterogeneous clastic formations from plastic–poroelastic deformation principles: theory and applications 
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下载免费PDF全文 Ran Bachrach 《Geophysical Prospecting》2017,65(3):724-735
Mechanical compaction or loss of porosity due to increase in effective stress is a fundamental geological process that governs many of the rock elastic and transport parameters, all of great importance in exploring and developing subsurface reservoirs. The ability to model the compaction process enables us to improve our understanding of the seismic signature of the basin and better relate the geology of deposition to current porosity, velocity, pore pressure, and other mechanical parameters that depend on the state of compaction of the sediment. In this paper, a set of mathematical equations that can be used to model the plastic deformation associated with primary and secondary loading curves is presented. Compaction laws are posed in terms of natural strain increment formulation often used in plasticity theory to model large deformation. Laboratory and field estimates of constitutive plastic deformation relations for sand–shale mixtures are used in a numerical model that generates estimates of porosity under various pore pressures, shale content, and loading scenarios. These estimates can be used in a variety of settings to predict various basin and reservoir properties associated with different loading conditions and/or sedimentation processes. 相似文献
46.
Mechanical compaction of sand-rich reservoirs usually occurs during shallow burial and involves the rearrangement of framework grains and the ductile deformation of soft lithoclasts. The reservoir quality (porosity and permeability) of some Neogene sandstones of the South Caspian Basin has, however, been dramatically reduced by mechanical compaction involving extensive grain-fracturing (i.e. porosity collapse). These sandstones were probably susceptible to pervasive grain-fracturing because they were buried rapidly and experienced compressional deformation prior to reaching 80 °C. Consequently, they did not undergo quartz cementation and were therefore exposed to high stresses while they were extremely weak. Grain-size and structural position are also important controls on the distribution of grain fracturing in the onshore analogue in the Apsheron Peninsula. Microstructural analysis confirms that susceptibility to distributed grain-fracturing increases with increasing grain-size. Structural position has also an important impact on the distribution of porosity collapse. In particular, sandstones within the hinges of folded sections have undergone much more extensive grain-fracturing than within the surrounding area; the increased stresses in this structural position have enhanced distributed grain-fracturing and subsequent deformation band development. 相似文献
47.
Facies controls on the distribution of diagenesis and compaction in fluvial-deltaic deposits 总被引：1，自引：0，他引：1
The Upper Triassic – Lower Jurassic Åre Formation comprising the deeper reservoir in the Heidrun Field offshore mid-Norway consists of fluvial channel sandstones (FCH), floodplain fines (FF), and sandy and muddy bay-fill sediments (SBF, MBF) deposited in an overall transgressive fluvial to lower delta plain regime. The formation has been investigated to examine possible sedimentary facies controls on the distribution of cementation and compaction based on petrography and SEM/micro probe analyses of core samples related to facies associations and key stratigraphic surfaces. The most significant authigenic minerals are kaolinite, calcite and siderite. Kaolinite and secondary porosity from dissolution of feldspar and biotite are in particular abundant in the fluvial sandstones. The carbonate minerals show complex compositional and micro-structural variation of pure siderite (Sid I), Mg-siderite (Sid II), Fe-dolomite, ankerite and calcite, displaying decreasing Fe from early to late diagenetic carbonate cements. An early diagenetic origin for siderite and kaolinite is inferred from micro-structural relations, whereas pore filling calcite and ankerite formed during later diagenesis. The Fe-dolomite probably related to mixing-zone dolomitization from increasing marine influences, and a regional correlatable calcite cemented layer has been related to a flooding event. Porosity values in non-cemented sandstone samples are generally high in both FCH and SBF facies associations averaging 27%. Differential compaction between sandstone and mudstone has a ratio of up to 1:2 and with lower values for MBF. We emphasize the role of eogenetic siderite cementation in reducing compactability in the fine-grained, coal-bearing sediments most prominent in MBF facies. This has implications for modeling of differential compaction between sandstone and mudstones deposited in fluvial-deltaic environments. 相似文献
48.
In an attempt to derive more information on the parameters driving compaction, this paper explores the feasibility of a method
utilizing data on compaction-induced subsidence. We commence by using a Bayesian inversion scheme to infer the reservoir compaction
from subsidence observations. The method’s strength is that it incorporates all the spatial and temporal correlations imposed
by the geology and reservoir data. Subsequently, the contributions of the driving parameters are unravelled. We apply the
approach to a synthetic model of an upscaled gas field in the northern Netherlands. We find that the inversion procedure leads
to coupling between the driving parameters, as it does not discriminate between the individual contributions to the compaction.
The provisional assessment of the parameter values shows that, in order to identify adequate estimate ranges for the driving
parameters, a proper parameter estimation procedure (Markov Chain Monte Carlo, data assimilation) is necessary. 相似文献
49.
Estimation of soil compaction parameters by using statistical analyses and artificial neural networks 总被引：2，自引：0，他引：2
This study presents the application of different methods (simple–multiple analysis and artificial neural networks) for the
estimation of the compaction parameters (maximum dry unit weight and optimum moisture content) from classification properties
of the soils. Compaction parameters can only be defined experimentally by Proctor tests. The data collected from the dams
in some areas of Nigde (Turkey) were used for the estimation of soil compaction parameters. Regression analysis and artificial
neural network estimation indicated strong correlations (r
2 = 0.70–0.95) between the compaction parameters and soil classification properties. It has been shown that the correlation
equations obtained as a result of regression analyses are in satisfactory agreement with the test results. It is recommended
that the proposed correlations will be useful for a preliminary design of a project where there is a financial limitation
and limited time. 相似文献
50.
Fault-propagation folding associated with an upward propagating fault in the Gilbertown graben system is revealed by well-based 3-D subsurface mapping and dipmeter analysis. The fold is developed in the Selma chalk, which is an oil reservoir along the southern margin of the graben. Area-depth-strain analysis suggests that the Cretaceous strata were growth units, the Jurassic strata were pregrowth units, and the graben system is detached in the Louann Salt.The growth trishear model has been applied in this paper to study the evolution and kinematics of extensional fault-propagation folding. Models indicate that the propagation to slip (p/s) ratio of the underlying fault plays an important role in governing the geometry of the resulting extensional fault-propagation fold. With a greater p/s ratio, the fold is more localized in the vicinity of the propagating fault. The extensional fault-propagation fold in the Gilbertown graben is modeled by both a compactional and a non-compactional growth trishear model. Both models predict a similar geometry of the extensional fault-propagation fold. The trishear model with compaction best predicts the fold geometry. 相似文献