Effective porosity

About: Effective porosity is a research topic. Over the lifetime, 1199 publications have been published within this topic receiving 26511 citations.

Prediction of porosity in the North Margin of the South China Sea

Abstract: Porosity is a very important parameter in rock physics and seismic prospecting.The porosity of water saturated sediments can be used to calculate elastic modulus and further velocities of primary and shear waves of sea-floor strata,identify hydrates,and estimate reserves of the hydrates.It is,however,often difficult to determine accurately the trend of porosity changes of unconsolidated sediments in the case without drilling data available.Several theoretical models have been proposed to calculate such porosity values based on the model that porosity decreases exponentially with depth,which requires some known parameters.It raises two problems: whether porosity indeed declines exponentially with depth;and how one chooses the proper parameters of the exponential model.In this paper,we suggest an alternative approach to solve this problem,in which the porosity of unconsolidated water-saturated sediments is calculated from surface downward layer by layer according to the sediment′s compaction,called the bulk modulus method.It only needs to know surface porosity and mineral composition of strata,thus favorable for saving the costs of exploration.We have applied this method to the South China Sea and in American ODP wells,and the results are well in agreement with logging data and seismic inversion results.

Determination of Effective-porosity Lower-limit for Changxing Reef Shoal Reser voir

Abstract: For Changxing reservoir,characterized by stronger heterogeneity,the porous structure is very complicatedSo,it is difficult to determine the lower limit of petrophysical-property parameters during reserve calculationIn this study,two methods of both deliverability simulation and minimum throat radius are presented based on an analysis on the petrophysical property of Changxing reef shoal reservoirThese two methods can be used to calculate the lower limitIn the first one,deliverability may be calculated through different producing pressure differential and reservoir thickness under formation simulation in lab;meanwhile,the lower limit can be determined by means of the relationship between production and porosity under the limit producing pressure differentialIn another one,the relationship between po rosity and throat radius is established based on the correlation of both petrophysical property and pore-throat size,and mercu ry-injection data;moreover,the porosity,corresponding to the minimum throat radius,is just the porosity lower limitThis limit of 20 %,calculated by these two methods,is roughly consistent with the result obtained from test and intersection method

Demarcation of hydrocarbon potential zones for Qishn clastic member, Masila oil field, Yemen

Abstract: The present study makes an attempt to utilize reservoir parameters which have been integrated into Arc GIS to delineate hydrocarbon potential zones in Masila oil field, Yemen. Petrophysical analysis has been carried out for a set of well logs data using Schlumberger Techlog software. Reservoir parameters calculated from well logs analysis include effective porosity (PHIE), permeability (K), Net-Pay thickness (N-PTh), hydrocarbon saturation (Sh), water saturation (Swe), the volume of shale (Vsh), and fault system (Fs). Petrophysical parameters prepared as contour maps, converted into raster format, classified and visualized as 2D/3D on GIS platform. Frequency ration model has been used to assess weighting score for each parameter with the help of existing wells location. Themes of reservoir parameters are reclassified by using weightage score of frequency ratio model. The result obtained from analyses of reservoir properties concluded that total effective porosity ranges between 17 and 38%, permeability between 108.89 and 903.30 mD, net-pay thickness 25–189.30 m, volume of shale 9–27%, water saturation 14–77%, and hydrocarbon saturation 73–86%, which is mostly concentrated in NW and SW in the study area. These parts of oil field reveal promising reservoir characteristics and have more hydrocarbon potential due to high values of permeability, porosity, and hydrocarbon saturation and less values of water saturation and volume of shale. The area is categorized into five potential zones, viz., very high, high, moderate, low, and very low. Reservoir cross plots of hydrocarbon occurrence have been used to validate the new potential zones. The result of overlay has shown very good correlation with the present ground situation. The outcome of this research will contribute to the development of the existing oil fields; besides, it will provide a superior database and will lead to improvement in decision-making to achieve higher hydrocarbon exploration and production.

Method for determination of permeability of shaly sand formation with low porosity and permeability based on efficient flow pore

Abstract: Since pore structure has a great effect on permeability of low porosity and permeability reservoirs,the permeability prediction with conventional parameters such as porosity and irreducible water saturation is of low accuracy. Based on the characteristic of fluid percolation in low porosity and permeability rock, the largest contribution of pores on fluid percolation is discussed and the concept of efficient flow pore introduced to improve accuracy of permeability. Samples with different shale content,porosity and permeability are selected, and experimental measurements are designed for the samples. The correlation coefficient of the permeability and the mercury-injection porosity corresponding to different pore radius is calculated from the mercury-injection experiment data. By making the plot of correlation coefficient and pore radius, radius cutoff of efficient flow pore is determined corresponding to a certain value of correlation coefficient( 0. 8),and the corresponding mercury-injection porosity as efficient flow porosity experimentally. On the basis of similarity of water and electric flow,the formula of efficient flow porosity is derived from conduction theory. Firstly,for water-bearing shaly sand with low porosity and permeability,the irreducible water and clay bound water are assumed as non-conducting matrix,and formation factor formula is derived with equivalent rock element model describing pore-throat ratio. Secondly,according to the definition,the efficient flow pore of the above-assumed rock with movable water pore only can be equivalent to curved capillary pore in the rock with the same volume and formation factor. The relation of formation factor and efficient flow porosity can be derived by curved capillary model.Finally,the expression of efficient flow porosity can be obtained by combining the two formulas. The values of parameters of the expression are optimized with the experimental data, and the calculation formula of efficient flow porosity is determined. The calculation formula of permeability of shaly rock with low porosity and permeability can be regressed with efficient flow porosity and permeability of the samples. The log data of well X1 and well X2 in low porosity and permeability reservoirs are processed with the proposed method. Comparison of calculated permeability from measuredpermeability shows that the method can improve the precision of permeability of low porosity and permeability reservoirs.