改进的开窗技术在利用测井资料预测渗透率中的应用

渗透率是油藏描述和油藏工程中一关键性的参数.文中描述了一种计算渗透率的新方法,即在岩心分析化验数据和相关测井曲线数据归一化的基础上,利用改进的开窗技术,借助反馈的神经网络方法逐点计算地层的渗透率.通过在胜坨油田的实际应用,证明该方法预测的渗透率与实际渗透率符合较好,具有推广应用的价值.     

低渗储层注水伤害研究

低渗透的宝浪油田是中偏强水敏储层,在进行了各种防膨措施后,注水压力仍不断上升,从25MPa上升至32MPa,依然欠注,即使频繁进行酸化、洗井等增注作业,效果也不理想。文章通过注入水水质分析和控含铁、含氧量进行的模拟地层水岩心流动驱替实验,认为注水造成储层堵塞的真正原因是注入水含铁含氧量偏高。注入水中含铁含氧,形成了Fe(OH)_2、Fe(OH)_3胶体,这类铁氧化合物,或包裹注入水中的固有颗粒,使颗粒粒径增大,形成"软颗粒",或产生新的颗粒,同注入水中的刚性颗粒相互作用,造成储层严重堵塞。即使少量的铁氧化合物,因低渗储层孔喉细小,其造成的堵塞也非常明显,在避免水敏的情况下,驱替120PV时伤害率达37.0%,而常规刚性颗粒堵塞,驱替180PV仅3.4%。所以,该低渗油藏注水开发,不但要防膨和控制注入水的颗粒粒径和颗粒浓度,尤为重要的是控制注入水的含铁、含氧量。     

裂隙岩体渗流参数讨论和渗流场有限元计算与分析

本文综合讨论了裂隙岩体渗流参数的特征,及由裂隙参数确定岩体渗透张量的过程。叙述了将岩体作为连续介质的三维非均质各向异性稳定渗流场有限元计算方法。通过对简单模型的有限元计算分析,讨论了各向异性渗流场的二个特征,即渗透主轴对渗流场的控制意义、以及渗透主轴与边界的关系对渗流场的控制意义。     

高温对混凝土孔隙率及渗透性影响的试验研究

简要评述了混凝土耐久性与孔隙率及渗透性的关系.通过采用纯酒精测试混凝土孔隙率;透氩气性能测试混凝土渗透性,并用Klinkenberg效应进行校正,试验研究了混凝土加热前后孔隙率及渗透性的变化.结果表明,混凝土受高温后,:孔隙率及渗透性明显增大,从而可证明其耐久性降低.     

Permeability differences based on three-dimensional geometrical information of void spaces

In this study,the permeabilities of Berea and Otway sandstones were measured under different confining pressures,and porosity was investigated through mercury intrusion porosimetry(MIP).The total porosities of the Berea and Otway sandstones were approximately 17.4%and 25%,respectively.Pore size distributions of each sandstone were almost the same,but the pores in the Otway sandstone were slightly narrower.However,the permeability of the Otway sandstone was smaller than that of the Berea sandstone by one order of magnitude.Three-dimensional(3D)void geometry and geometrical properties of the void spaces relevant to flow were compared to obtain the relation between the permeability differences and porosities of the two sandstones.The 3D geometrical analysis using microfocus X-ray computed tomography(CT)was performed,and the pore geometries of both sandstones were compared using the 3D medial axis(3DMA)method.Pore and throat radii,pore coordination number,tortuosity,number of connecting paths,connecting path volume,and other factors were determined using 3DMA.The Otway sandstone was characterized by a small effective throat/pore radius ratio.Based on the fluid flow mechanism,the lower effective throat/pore radius ratio results in a lower permeability induced by the fluid energy loss,which means that the 3D geometrical shape of void spaces affects the permeability value.     

TRANSPORT PROPERTIES OF CELLULAR FOOD MATERIALS UNDERGOING FREEZE-DRYING

The samples of sliced and mashed apples were freeze-dried by controlling their surface temperatures over the usual pressure range of commercial operations. The surface of sliced samples could not be maintained at above 10°C in order to prevent the frozen layer from melting, while that of mashed samples was allowed to heat up to 70°C.

Thermal conductivities and permeabilities were determined by applying the uniformly-retreating-ice front model to the dried layer of the samples undergoing freeze-drying. The values of permeability for the mashed samples were found to depend on the ice-crystallization time during freezing. The results indicated that the drying rate of sliced samples was limited by the transfer rate of water vapor flowing through the dried layer. A cellular structural model is proposed for predicting the permeability of the dried layer, based on the resistance of the cell membrane to molecular transfer of water vapor.     

Influence of High-Permeability Layers for Enhancing Landfill Gas Capture and Reducing Fugitive Methane Emissions from Landfills

Gas collection systems of various designs have been used to control landfill gas emissions, which can be problematic, particularly before installation of final landfill covers. In this work, an innovative gas collection system that includes a permeable layer near the top surface of landfills was evaluated for enhancing capture of landfill gas and reducing fugitive methane emissions. A computational model that accounts for advective and diffusive fluxes of multiple gas components was used to evaluate the efficiency of this new design for intermediate landfill covers. The utility of the high-permeability gas-conductive layer was illustrated for several conditions of interest including varying refuse permeability, varying degrees of permeability anisotropy, and temporal atmospheric pressure changes. Simulations showed that the permeable layer decreased methane emissions by 43% when the horizontal to vertical permeability ratio for refuse was kh/kv = 3 and the domain average kh = 3×10?12?m2, while reductions in methane emissions decreased to 17% for the same anisotropy but with kh = 10?11?m2. With this design, barometric pressure changes did not significantly affect oxygen intrusion or methane emission rates.     

A Flat Polymeric Membrane Sensor for Carbon Dioxide/Nitrogen Gas Mixture

A gas sensor was developed to measure the concentration of binary gas mixtures. This sensor works based on the permeability change of different gas mixtures across the polymeric membranes. Although high values of permeability and selectivity are needed for an ideal separation, the performance of this sensor mainly depends on the permeability factor. Polysulfone and silicone rubber were applied as the membrane base and coat, respectively. Moreover, in contrast to existing polymeric sensors that use hollow fibers, the present sensor is made of flat membranes. This new design is cheaper, smaller, and easier to use in comparison to the hollow fiber polymeric sensors. In order to test the sensor applicability, nitrogen and carbon dioxide were used as model gases. The effect of pressure on the response time and sensor accuracy was studied for the aforementioned gases. The response time (T_95%) of this low price sensor was 50?s, and the tolerance of measuring concentration was approximately 1.4% at 2?bar feed pressure. Also, increasing the feed pressure can improve the response time or accuracy of the sensor.     

Diffusive Transport of VOCs through LLDPE and Two Coextruded Geomembranes

The diffusive properties of two coextruded geomembranes, one with a polyamide inner core and the other with an ethylene vinyl-alcohol (EVOH) inner core, and a standard 0.53-mm (20-mil) linear low-density polyethylene (LLDPE) geomembrane were examined. Diffusion and sorption laboratory tests were performed to estimate the parameters controlling diffusive migration, including the partitioning, diffusion, and permeation coefficients of the geomembrane in both the aqueous and vapor phases. Results indicate a significant reduction in mass flux through the coextruded geomembranes compared to conventional LLDPE. The EVOH coextruded geomembrane had the lowest permeation coefficients (Pg) with a range of (2–6)×10?12?m2?s?1 for diffusion from the aqueous phase. These values for EVOH are upper bounds and the actual values may be lower than as stated. The polyamide (nylon) coextruded geomembrane had higher values than for EVOH, with a Pg range of (0.7–2.2)×10?11?m2?s?1 from the aqueous phase. The highest permeation coefficients were for the standard 20-mil LLDPE, which ranged from (0.6–1.1)×10?10?m2?s?1. Thus the permeation coefficient for LLDPE was about one order of magnitude greater than for the nylon coextruded and at least two orders of magnitudes higher than for the EVOH coextruded geomembrane. Both coextruded geomembranes showed decreased Pg values and therefore improved diffusive resistance to volatile organic compounds over traditional 0.56-mm PVC geomembranes. The EVOH geomembrane showed a 5–12-fold decrease in Pg in comparison to a 2.0-mm high density polyethylene geomembrane.