A detailed study of the productivity and recovery potential for a turbidite reservoir has been completed using a practical application of stochastic modeling and reservoir simulation techniques. The objective of this study was to assess the impact of various reservoir characteristics on development considerations such as well spacing and expected production/recovery profiles. Distributions of typical sand body dimensions were estimated from a review of core, log, seismic, and analog data. These distributions were input to a stochastic modeling program to generate multiple realizations of reservoir descriptions for a range of net/gross ratios, facies distributions, and assumed sand body geometries. An interface program was developed to minimize the gridding problems associated with conversion of stochastic model output to reservoir simulation input data. Grid data generated from this program were input directly to practically sized reservoir simulation models. Results from the stochastic realizations and simulation models demonstrated the potential variability in connectivity and recovery profiles that may be expected for a turbidite reservoir. The reduced connectives in the stochastic model yield significantly different production profiles and lower recoveries than would be calculated with the assumption of continuous layer-cake type models. The approach developed for this study can be used to define and improve confidence limits for production and recovery profiles from typical turbidite reservoirs with only limited well information. Introduction Turbidite reservoirs are formed as a result of downslope movements of clasic sediments under the forces of gravity and fluid turbulence. These reservoirs are generally associated with deep sea submarine fans. Typical deposits consist of massive, structureless channel fill sands which pass laterally into and are overlain by progressively thinner, laminated intervals of sands and shales. The shifting, stacking, and erosion of these channel-levee systems results in a complex reservoir description with variable correlation of individual sands at the scale of typical well spacing. Interchannel areas, which are often dominated by muds (shales) and thin-bedded sands, can significantly reduce the connectivity of individual sand sequences. A schematic illustration of a typical facies distribution for this type of turbidite system is presented in Figure 1. An assessment of the impact of sand discontinuities or connectives in these reservoirs is required for realistic performance predictions and estimation of associated confidence limits. This is particularly important during the pre-development stage when major investment decisions, regarding well spacing and facility (platform) requirements, are being made on the basis of a limited number of exploration wells. Analytical calculations and conventional simulation approaches based on layer-cake type models will lead to optimistic results. Alternate model representations were proposed by Weber and van Geuns in which the architecture of middle and upper fan turbidites was described as either "jigsaw" or "labyrinth" distributions of sand bodies. P. 343^
Pore volume compressibilities have a major impact on recovery estimates for unconsolidated sand reservoirs. A realistic estimate of the recovery factors is imperative to prospect development decisions. Confirmation of higher pore volume compressibilities may lead to development of new discoveries or preclude secondary recovery measures in complicated reservoir systems. By performing a pulse test at the East Breaks 165 field, an "in situ" measurement of pore volume compressibility for a producing Gulf of Mexico unconsolidated reservoir was obtained to verify the large compressibilities measured from uniaxial core testing. The pulse test was run between two East Breaks 16S wells. High quality pressure data was obtained, and the formation’s diffusivity and transmissivity were determined. To extract the formation’s pore volume compressibility from the test data, key components of the reservoir had to be suitably identified. PVT work was required to confirm that the reservoir was not originally at its bubble-point as first assumed, and therefore, no free gas was present in the system to mask the pore volume compressibility. In addition, the approximated reservoir thickness produced an unrealistic estimate of pore volume compressibility. Consequently, a production log was run in the puiser well indicating that two-thirds of the perforated interval was not contributing to flow. Utilizing this additional information, the final pore volume compressibility derived from the pulse test compared favorably with the core data. An outgrowth of this investigation was a better understanding of the suspected formation damage believed to be caused by fines migration. Interpretation of the related pressure build-ups reflected extremely high damage in both welk. The production log and a subsequent pulse neutron log confirmed the probability of significant fines movement in the formation. These results substantiated the deterioration of well productivity observed over the past three years. Identification of near wellbore damage and its cause will allow appropriate remedial work to recover lost well capacity and maximize reserves recovery.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.