Effective porosity

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

Oil layer recognition method based on tight reservoir conductive factor experiment

Abstract: The invention provides an oil layer recognition method based on a tight reservoir conductive factor experiment. The method comprises the steps of 1, obtaining horizontal rock cores of different depths of a reservoir; 2, obtaining the porosity and permeability of the horizontal rock cores, and calculating quality indexes; 3, measuring the specific resistance of the horizontal rock cores and the specific resistance of saturated salt water, and obtaining formation factors; 4, conducting nuclear magnetic resonance measurement to obtain a T2 spectrum, the total porosity, the effective porosity and the irreducible water saturation; 5, conducting an X diffraction and casting body thin section experiment; 6, according to the measurement and experiment results, building the relevant relationship between the formation factors and factors comprising the total porosity, the effective porosity, the pore throat size, distribution, connectivity and the like; 7, on the basis of the built relevant relationship, determining an oil layer recognition algorithm, and conducting oil layer recognition on the reservoir. By utilizing the oil layer recognition method, the reservoir conductive capacity and the factors affecting the reservoir conductive capacity can be analyzed according to tight reservoir experiment data, and the oil layer reservoir algorithm of the tight reservoir is determined according to the analyzed result.

Borehole Nuclear Magnetic Resonance: Experience and Reservoir Applications in West Kuwait Carbonate Reservoirs

Abstract: Recently introduced nuclear magnetic resonance well logging has been tested and evaluated in West Kuwait and is now being used to better define effective reservoir porosity in the most complicated reservoirs and under difficult conditions, including oil-base drilling muds. A number of West Kuwait carbonate oil reservoirs are difficult to evaluate because of the complexities of their pore systems. Borehole imagery has helped to define fractures and faults in wells and, thus remove a major uncertainity in formation evaluation. Standard open hole well logs provide porosity and saturation which are often not enough in evaluating these complex carbonate reservoirs with high-resistivity. In fact, apparent porosity and saturation may be misleading as to what fluids and at what rates will flow from a given zone. Low porosity layers can have the highest permeability within a reservoir and similarly the highest porosity layer may be comprised of micropores and be impermeable. Moreover, zones which correctly calculate high water saturation with standard well logs may flow oil with no water while tar mats may be misleadingly interpreted as an oil zone. Borehole nuclear magnetic resonance helps to define the potential of the most complex carbonate reservoirs in West Kuwait. Borehole NMR, in addition to providing porosity independent of lithology, can be related to pore size once hydrocarbon effects are accounted for. Understanding pore size distribution within a reservoir helps to define effective porosity, identifies the presence of microporosity and quantifies irreducible water saturation when used with standard well log evaluation. The definition of effective porosity and pore size distribution allow better determination of reserves. Initial estimates of permeability without any modeling of specific reservoir rock types have related well to the independent assessment of permeability by acoustic technique and wireline formation testing. Our assessment of borehole nuclear magnetic resonance has been very encouraging. It has been possible to use borehole NMR to better identify reservoir facies, predict well productivity and select completion zones. Many other reservoir and geological applications are being examined at present time.

Application of seismic post-stack inversion for gas reservoir delineation: A case study of Talang Akar Formation, South Sumatera Basin

Abstract: Nauli Field is one of the marginal fields that is located in the western region of Indonesia and has been proven to produce oil and gas hydrocarbons. The field is located in the South Sumatra Basin with reservoir target is sandstone from Talang Akar Formation. The purpose of this study is to integrate petrophysical interpretation and seismic data analysis. Reservoir characterization was performed based on porosity and water saturation for each layer within the wells. Seismic inversion methods chosen to estimate the attributes of P-impedance (Zp), S-impedance (Zs) and density (ρ). Amplitude Versus Offset (AVO) inversion through Lambda-Mu-Rho (LMR) attribute can provide information on lithology and fluids content in the reservoirs. The connection between seismic inversion and AVO inversion was to validate the gas content from the seismic data and its lateral dispersion. Data processing and analysis shows that the effective porosity for Nauli Field is between 10 to 20 porosity unit (p.u) with 20-70% water saturation. The thickness of net pay is 2-8 meters. Post-stack inversion shows impedance anomaly around 1580-1590 ms with value 22.000-25.000 (m/s)*(g/cc). Petrophysical analysis estimated this anomaly as layer-x sandstone with gas fluid saturated. LMR attribute confirm this fluid with lower Lambda-Rho values around 11-20 (Gpa)*(g/cc) than Lambda-Rho values around 28-32 (Gpa)*(g/cc).

Application of Petrophysically Derived "Flow Facies" for Reservoir Characterization and Simulation: Wara Reservoir, Greater Burgan Field

Abstract: In fluvially dominated delta plain reservoirs, such as the Wara formation in the Greater Burgan Field, characterizing a reservoir's flow properties accurately is essential in developing a sound reservoir model. This is easier said than done. Typically, lithofacies identified in cores are correlated to multiple log suite characteristics. These are then used to help define simulation flow properties in wells. In Greater Burgan, with over fifty years of production, much of the field development occurred before modem diagnostic logging tools became available. Therefore, direct correlation of core lithologies and corresponding lithofacies description to multilog character is not possible in the majority of wells. Relationships discovered between shale volume (V SH ) ranges and effective porosity (o eff ) to permeability transforms allowed us to apply unique rock properties to flow units or facies defined by the V SH -porosity ranges. These flow facies eliminated the difficult task of trying to predict changing lithologies and lithofacies in wells with limited log traces and no core.

Simulation of ground-water flow in steep basin with shallow surface soil

Abstract: A coupled ground-water/channel flow distributed model has been developed for continuous simulation in a 123-km 2 basin. The aim was to analyze the streamflow generation processes in natural vegetated environments. Finite-difference schemes have been used to solve conservation equations of the 2D saturated subsurface flow and the 1D kinematic surface flow. Because of the high hydraulic conductivity of the surface soil, only the saturation excess mechanism of runoff production has been considered. Parameter sensitivity analysis showed the overriding influence of soil storage capacity and conductivity. A grid discretization >100 m produces a hydraulic conductivity greater than physically meaningful, which considerably increases as the space-grid step increases. Results indicate that the model can satisfactorily simulate the water-flow behavior of the catchment after fitting the three parameters of surface hydraulic conductivity, effective porosity, and evapotranspiration losses. These are done after calculating the conductivity as a function of the height of the water table. The simulation efficiency has varied from 87% in the first 5-year calibration period to 85.8% in the subsequent 5-year validation period.