Browsing by Subject "porosity"
Now showing 1 - 5 of 5
Results Per Page
Sort Options
Item Acoustic impedance inversion of the Lower Permian carbonate buildups in the Permian Basin, Texas(Texas A&M University, 2004-11-15) Pablo, Buenafama AlemanCarbonate reservoirs are usually diffcult to map and identify in seismic sections due to their complex structure, lithology and diagenetic frabrics. The Midland Basin, located in the Permian Basin of West Texas, is an excellent example of these complex carbonate structures. In order to obtain a better characterization and imaging of the carbonate buildups, an acoustic impedance inversion is proposed here. The resolution of the acoustic impedance is the same as the input seismic data, which is greatly improved with the addition of the low frequency content extracted from well data. From the broadband volume, high resolution maps of acoustic impedance distributions were obtained, and therefore the locations of carbonate buildups were easily determined. A correlation between acoustic impedance and porosity extracted from well data shows that areas with high acoustic impedance were correlated with low porosity values, whereas high porosities were located in areas of low acoustic impedance. Theoretical analyses were performed using the time-average equation and the Gassmann equation. These theoretical models helped to understand how porosity distributions affect acoustic impedance. Both equations predicted a decrease in acoustic impedance as porosity increases. Inversion results showed that average porosity values are 5% [plus or minus] 5%, typical for densely cemented rocks. Previous studies done in the study area indicate that grains are moderately to well-sorted. This suggests that time-average approximation will overestimate porosity values and the Gassmann approach better predicts the measured data. A comparison between measured data and the Gassmann equation suggests that rocks with low porosities (less than 5%) tend to have high acoustic impedance values. On the other hand, rocks with higher porosities (5% to 10%) have lower acoustic impedance values. The inversion performed on well data also shows that the ?uid bulk modulus for currently producing wells is lower than in non-productive wells, (wells with low production rates for brine and hydrocarbons), which is consistent with pore ?uids containing a larger concentration of oil. The acoustic impedance inversion was demonstrated to be a robust technique for mapping complex structures and estimating porosities as well. However, it is not capable of differentiating different types of carbonate buildups and their origin.Item An alternative to the Winland R35 method for determining carbonate reservoir quality(Texas A&M University, 2008-10-10) Lafage, Stephanie IsabelleThe Winland R35 method [Log R35 = 0.732 + 0.588 (Log Kair) 0.864 (Log O)] is based on the relationship between porosity, permeability, and pore throat radius at the point of 35% mercury saturation in capillary pressure measurements and is generally reliable in rocks with only intergranular porosity (such as sandstone) where pore and pore throat geometry are related closely to rock texture. Carbonate pores are not always so; consequently, the Winland method is not as reliable for assessing reservoir quality in carbonate reservoirs. To evaluate alternatives to the conventional Winland technique, based on rock facies characteristics, samples from the Jurassic Smackover Formation in Alabama and the Permian Clearfork Formation in Texas were tested for reservoir quality with use of the Winland R35 and Pittman methods to determine if either method is more reliable in carbonate reservoir studies. Pittman's modification of the Winland method was found to be more accurate graphically. A third method for evaluating reservoir rock character is provided by Lucia. This method is based on geological rather than petrophysical characteristics, and it revealed that pore throat sizes at 35% mercury saturation may include a variety of depositional and diagenetic rock fabrics. The Winland and Pittman petrophysical evaluation techniques, as well as the Lucia geological evaluation technique - when based on depositional facies alone - do not provide reliable measures of reservoir quality. An alternative method based on genetic pore type presented by Ahr in 2005 was tested for comparison. Using a porosity-permeability plot based on the pore type, the relationship between porosity, permeability, and pore type was found to be strong and reproducible. When the ratio of permeability to porosity was used in combination with Ahr genetic pore types, the results indicate that barriers, baffles, and flow units can be reliably defined. This study demonstrates that the use of pore types in conjunction with capillary pressure measurements is a more reliable method for evaluating carbonate reservoirs than any alternative method that is based on depositional facies or rock fabrics alone.Item Evaluation of Ti-6Al-4V Parts Produced with Rapid Prototyping Technology: Electron Beam Melting Machine(2014-09-29) Abdeen, DanaThe present study measured the corrosion properties of Ti-6Al-4V parts produced with Electron Beam Melting machine (EBM). Potentiodynamic and potentiostatic tests were applied on EBM Ti-6Al-4V in 3.5% mass NaCl solution, to determine the pitting potential and critical pitting temperature (CPT). A relation between pitting potential and temperature was established for EBM Ti-6Al-4V alloy by conducting potentiodynamic test under different temperatures from room temperature until 83?C. Critical pitting temperature was also measured in 3.5% mass NaCl solution of different pH of 2.0, 5.7 and 10.0, to examine the effect of aggressive conditions on the pitting corrosion of EBM alloy. Moreover, the same tests were performed on wrought Ti-6Al-4V for comparison purposes. The results showed that EBM alloy maintained its corrosion resistance as it had the same pitting potential of wrought alloy even at higher temperatures. EBM alloy did not pit when performing potentiostatic test at 800 mV vs. Saturated Calomel Electrode (SCE) even under different pH of the solution. Due to the manufacturing technique and conditions of the EBM machine, the resulted object has irregularities on the exterior surface and voids that are formed within the part which affects samples? properties like surface roughness, CPT, density and porosity. In this study, a statistically designed experiment was employed to manufacture Ti-6Al-4V samples in EBM machine under different process parameters of beam current, beam speed and offset focus. Surface roughness was measured for as-built samples. Then, a potentiostatic test was conducted under 2.40 V vs. SCE to determine the critical pitting temperature in 3.5 % mass NaCl solution for the same samples of different processing parameters. Moreover, density was measured and porosity was calculated from density values. Finally, a model equation was established in order to relate EBM?s process parameters to measured properties of surface roughness, CPT, density and porosity. It was noted that offset focus had the main influence on surface roughness more than beam current and beam speed. Changing processing parameters did not affect corrosion behavior of EBM Ti-6Al-4V as CPT did not vary widely, with a slight effect obtained from beam current and beam speed. Density and porosity were greatly affected with offset focus more than the other parameters. It can be concluded that uniform and precise roughness and porosity are not achievable through this machine, only a range of these properties can be attained.Item Identification of pore type and origin in a Lower Cretaceous carbonate reservoir using NMR T2 relaxation times(Texas A&M University, 2004-09-30) Lodola, Domenico DomenicoDetermining the distribution of porosity and permeability is one of the main challenges in carbonate petroleum reservoir characterization and requires a thorough understanding of pore type and origin, as well as their spatial distributions. Conventional studies of carbonate reservoirs require interpretation and analysis of cores to understand porosity. This study investigates the use of NMR logs in the determination of pore type and origin. This study is based on the analysis of both thin section petrographic and NMR data from a single well that cored the Lower Cretaceous (Aptian) shelf carbonates belonging to the Shuaiba Formation of the Middle East. Photographs of thin sections were used to determine pore type and origin according to Ahr's genetic classification of carbonate porosity. Descriptive statistics and modeling were used to analyze the NMR T2relaxation time distributions. Descriptive statistical analyses included estimating arithmetic average, standard deviation, skewness, median, mode and 90th percentile. T2modeling was performed by fitting multiple log-normal distributions to the measured T2distribution. Data from thin section petrography and from NMR measurements were then compared using conditional probabilities. As expected, thin section analysis revealed the predominance of mud-supported fabrics and micropores between matrix grains Vugs and dissolved rudistid fragments account for most of the macro porosity. Descriptive statistics showed that the mode and th percentile of the T2distribution had the greatest power to discriminate pores by origin. The first principal component (PC1) of the mode-90th percentile system was then used to compute the probabilities of having each pore origin, knowing that PC1 belongs to a given interval. Results were good, with each origin being predictable within a certain range of PC1. Decomposition of the T2distributions was performed using up to 3 log-normal component distributions. Samples of different pore origin behaved distinctively. Depositional porosity showed no increase in fit quality with increasing number of distributions whereas facies selective and diagenetic porosity did, with diagenetic porosity showing the greatest increase.Item Interpretation, Analysis and Design of Inter-well Tracer Tests in Naturally Fractured Reservoirs(2013-08-19) Alramadhan, Aymen AbduljalilIn order to understand the complex fracture network that controls water movement in Sherrod Area of Spraberry Field in West Texas and to better manage the on-going waterflood performance, a field scale inter-well tracer test was implemented. This test presents the largest inter-well tracer test in naturally fractured reservoirs reported in the industry and includes the injection of 13 different tracers and sampling of 110 producers in an area covering 6533 acres. Sherrod tracer test generated a total of 598 tracer responses from 51 out of the 110 sampled producers. Tracer responses showed a wide range of velocities from 14 ft/day to ultra-high velocities exceeding 10,000 ft/day with same-day tracer breakthrough. Re-injection of produced water has caused the tracers to be re-injected and added an additional challenge to diagnose and distinguish tracer responses affected by water recycling. Historical performance of the field showed simultaneous water breakthrough of a large number of wells covering entire Sherrod area. This research investigate analytical, numerical, and inversion modeling approaches in order to categorize, history match, and connect tracer responses with water-cut responses with the objective to construct multiple fracture realizations based entirely on water-cut and tracers? profiles. In addition, the research highlight best practices in the design of inter-well tracer tests in naturally fractured reservoirs through lessons learned from Sherrod Area. The large number of tracer responses from Sherrod case presents a case of naturally fractured reservoir characterization entirely based on dynamic data. Results indicates that tracer responses could be categorized based on statistical analysis of tracer recoveries of all pairs of injectors and producers with each category showing distinguishing behavior in tracers? movement and breakthrough time. In addition, it showed that tracer and water-cut responses in the field are dominantly controlled by the fracture system revealing minimum information about the matrix system. Numerical simulation studies showed limitation in dual porosity formulation/solvers to model tracer velocities exceeding 2200 ft/day. Inversion modeling using Gradzone Analysis showed that east and north-west of Sherrod have significantly lower pore volume compared to south-west.