Browsing by Subject "Hydrocarbon reservoirs--Mexico, Gulf of"
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Item A field study to assess the value of 3D post-stack seismic data in forecasting fluid production from a deepwater Gulf-of-Mexico reservoir(2005) Gambús Ordaz, Maika Karen; Torres-Verdín, CarlosThis dissertation describes a study undertaken to appraise the reliability of spatially complex hydrocarbon reservoir models constructed with the use of 3D post-stack seismic amplitude data and well logs. Developments center about the interpretation of data acquired in an active hydrocarbon field in the deepwater Gulf of Mexico. The availability of measured time records of fluid production and pressure depletion provides an independent way to quantify the accuracy and reliability of several methods commonly employed to construct static reservoir models. We make use of geostatistical inversion to construct spatial distributions of porosity and permeability that simultaneously honor well logs and 3D poststack seismic amplitude data. The constructed reservoir models are compared against models constructed with standard geostatistical procedures that do not make use of seismic amplitude data or else that use a simple statistical correlation between reservoir properties and seismic - inverted acoustic impedances. We perform multi-phase fluid-flow simulations to assess the consistency of the constructed reservoir models against the measured time record of flow rates of gas/water and shut-in well pressures. For the hydrocarbon field under consideration, the joint stochastic inversion of well logs and 3D post-stack seismic amplitude data consistently yields the closest match to dynamic measurements of fluid production and pressure depletion. Our study also compares the influence of petrophysical and rock-fluid parameters on the reliability and accuracy of the predicted fluid production against the influence of spatial variability of porosity and permeability.Item Influence of reservoir character and architecture on hydrocarbon distribution and production in the miocene of Starfak and Tiger Shoal fields, offshore Louisiana(2002-12) Rassi, Claudia; Fisher, William L.Reservoir properties and production performance have been assumed to be controlled by their sequence stratigraphic position and the systems tract in which they are found. This hypothesis has been tested in a dataset from two mature gas fields, located ten miles offshore Louisiana. Available data included several decades of production history, various geophysical logs of 155 wells, sidewall core and special core analyses, which provide full information on hydrocarbon distribution and type, reservoir lithology, porosity, permeability, and production characteristics. The systems tracts of the Miocene study interval (60 fourth-order and 10 third-order sequences) were characterized with thickness and net sand maps, facies interpretation, and production evaluation. The three systems tracts of the fourth-order sequences (lowstand, transgressive, and highstand) show different trends in rock properties, such as porosity, permeability, or sand content. Each systems tract can be characterized with a typical range of values for its reservoir properties. These reservoir characteristics are clearly different for each of the three fourth-order systems tracts. In contrast, the data of the third-order sequences show high variability. The values of porosity of the three systems tracts do not differ significantly from each other and prediction is impossible with high confidence. The sequence stratigraphic framework was linked to production information by (1) analyzing the average monthly production rate per perforated foot of fourth-order systems tracts and by (2) correlating to producing facies of each fourth-order systems tract. The strongest producers were found in facies of lowstand and highstand systems tracts and ranked highest. The incorporation of depositional facies interpretation into the fourth-order framework allows more detailed production estimation. Facies data also confirm the general picture of the systems tracts regarding rock properties, but they reveal differences among the facies types that could not be detected during the analysis of entire fourth-order systems tracts. One end product of this research is a database that stores all the information collected during the research, with customized search options that present a quick overview of systems tracts information. The application of this database is limited to stratigraphic units produced by similar depositional environments.Item Spatial delineation, fluid-lithology characterization, and petrophysical modeling of deepwater Gulf of Mexico reservoirs through joint AVA deterministic and stochastic inversion of 3D partially-stacked seismic amplitude data and well logs(2006) Contreras, Arturo Javier; Fisher, William L.; Torres-Verdin, CarlosThis dissertation describes a novel Amplitude-versus-Angle (AVA) inversion methodology to quantitatively integrate pre-stack seismic data, well logs, geologic data, and geostatistical information. Deterministic and stochastic inversion algorithms are used to characterize flow units of deepwater reservoirs located in the central Gulf of Mexico. A detailed fluid/lithology sensitivity analysis was conducted to assess the nature of AVA effects in the study area. Standard AVA analysis indicates that the shale/sand interface represented by the top of the hydrocarbon-bearing turbidite deposits generate typical Class III AVA responses. Layer-dependent Biot-Gassmann analysis shows significant sensitivity of the P-wave velocity and density to fluid substitution, indicating that presence of light saturating fluids clearly affects the elastic response of sands. Accordingly, AVA deterministic and stochastic inversions, which combine the advantages of AVA analysis with those of inversion, have provided quantitative information about the lateral continuity of the turbidite reservoirs based on the interpretation of inverted acoustic properties and fluid-sensitive modulus attributes (PImpedance, S-Impedance, density, and LambdaRho, in the case of deterministic inversion; and P-velocity, S-velocity, density, and lithotype (sand-shale) distributions, in the case of stochastic inversion). The quantitative use of rock/fluid information through AVA seismic data, coupled with the implementation of co-simulation via lithotype-dependent multidimensional joint probability distributions of acoustic/petrophysical properties, provides accurate 3D models of petrophysical properties such as porosity, permeability, and water saturation. Pre-stack stochastic inversion provides more realistic and higher-resolution results than those obtained from analogous deterministic techniques. Furthermore, 3D petrophysical models can be more accurately co-simulated from AVA stochastic inversion results. By combining AVA sensitivity analysis techniques with pre-stack stochastic inversion, geologic data, and awareness of inversion pitfalls, it is possible to substantially reduce the risk in exploration and development of conventional and non-conventional reservoirs. From the final integration of deterministic and stochastic inversion results with depositional models and analogous examples, the M-series reservoirs have been interpreted as stacked terminal turbidite lobes within an overall fan complex (the Miocene MCAVLU Submarine Fan System); this interpretation is consistent with previous core data interpretations and regional stratigraphic/depositional studies.