Accurate Oil Saturation Determination and Monitoring in a Heavy Oil Reservoir

Harness, P.E.; Shotts, Noel; Hemingway, Jim; Rose, D. V.; Sluis, Lidewey E. C. van der

doi:10.2523/46245-ms

Cited by 3 publications

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“…Por se tratar de técnica difundida e aprovada pela indústria, diversos trabalhos podem ser encontrados, dentre os quais o de Harness et al (1998) na determinação e monitoramento de óleo pesado no campo maduro de Kern River, Estados Unidos; Elshahawi et al (2001) no monitoramento da saturação de óleo no Golfo de Suez e Moinard et al (2001), que estuda o monitoramento da saturação do reservatório do Campo de Attaka, Bacia Kutei, Indonésia. Harness et al (1998) defende o uso na determinação da saturação e monitoramento da depleção do reservatório, sendo também de grande valia no monitoramento dos poços, propiciando maior precisão e atualização dos dados de saturação do campo, gerando assim a possibilidade de um gerenciamento mais eficaz e planos futuros de adensamento da malha exploratória. De acordo com Elshahawi et al (2001), o uso no monitoramento da saturação de água é de grande valia pois não sofre influência da salinidade da água, ao contrário das ferramentas desenvolvidas para a quantificação de saturação de gerações anteriores.…”

Section: Histórico De Utilização Da Ferramenta E Trabalhos Relacionadosunclassified

Tecnicas geoestatisticas aplicadas na modelagem da saturação de oleo

Zanão¹

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Degree).Cased well logging with tools which quantify the water saturation had been done in the Study Field, located on Recôncavo Basin, considered mature and with reminiscent hydrocarbonates storage in the Sergi Formation. The geostatistical techniques of ordinary kriging and kriging with external drift had been used to the studied field for porosity and water saturation of development model. The results of the modeling of water saturation variable in steps of time allowed to characterized the evolution of the water saturation in the field and the identification of the remaining oil portions. With information models of petrophysics and the fluids saturation , the oil volume calculus for the three temporal intervals analyzed had been done. Values had been obtained which allowed proving the dynamic of Sw variable along the years and verifying the reminiscent oil in the reservoir.

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Section: Histórico De Utilização Da Ferramenta E Trabalhos Relacionadosunclassified

Tecnicas geoestatisticas aplicadas na modelagem da saturação de oleo

Zanão¹

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Is Accurate Gas/Steam Determination Behind Pipe Feasible with Pulsed Neutron Measurements?

Badruzzaman

Crowe

Bean

et al. 2007

Asia Pacific Oil and Gas Conference and Exhibition

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Pulsed neutron measurements are commonly used to locate gas behind casing and quantify steam saturation, but do not always yield desired results. Several parameters are utilized to identify gas and one parameter, the thermal neutron capture cross section, Sigma, is used to compute steam saturation. In the paper we report a mixed experience in identifying gas with these techniques, across fields, tools and vendors. Some parameters have worked well in some cases but have performed poorly in others. The uncertainty in steam saturation, computed using Sigma, is greater than those previously reported elsewhere. Modeling offers insight into the mixed results. It appears that in some cases the PNC-derived Sigma may yield erroneous steam saturation for a variety of reasons, including uncertainties in the input parameters and possibly an inherent nonlinear transport effect that increases as steam saturation increases. An alternative approach based on PNC pseudo-porosity is explored. Calibration of cased-hole tools in gas reservoirs, generic and local, open-hole baseline data and core analysis of complex rocks are essential. Currently, these are either nonexistent or infrequent. Introduction Pulsed neutron capture (PNC) technique, initially used to compute water saturation in high- salinity reservoirs (for example, Dewan, et al., 1973) and in log-inject-log experiments to determine residual oil saturation, was extended to locate gas (Blackburn and Brimage, 1978). It is increasingly being utilized to locate gas in complex conditions and quantify steam saturation in steam floods. In addition, inelastic data, normally used to compute oil saturation, are being used to complement PNC techniques to detect gas. Recent applications in complex conditions include:identification of gas caps to optimize perforation decisions and reduce production of associated gas in West Africa (Badruzzaman, et al., 1997),monitoring steam-chest growth and estimation of steam saturation in steam floods in California and Indonesia (Badruzzaman, et al., 1998; Harness et al., 1998; Zalan, et al., 2003.),locating shallow gas hazards in Gulf of Thailand (Pathanakitchakarnjaroen, et al., 2005) andlocation of pay and identification of swept gas zones in Gulf of Mexico. The technique is being considered to monitor CO2 sequestration in Australia. In addition to PNC techniques, inelastic counts have been utilized as an independent validation of gas behind pipe. Success with pulsed neutron (PN) techniques, involving either the capture or inelastic interactions, has been mixed. Location of gas cap to reduce production of associated gas has generally been successful in Nigeria. Monitoring steam growth with PNC techniques has been successful in steam floods in California and Indonesia. Quantification of steam saturation has been very accurate in California while less so in Indonesia. Locating shallow gas hazards in the Gulf of Thailand has been ambiguous. Pay identification in Gulf of Mexico has been usually clear, but not always.

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Assessing the Capabilities of a Cased-Hole Reservoir Analysis System in the Gulf of Thailand

Odom¹,

Platt²,

Pavlakos³

2000

SPE Asia Pacific Oil and Gas Conference and Exhibition

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The option of using a cased-reservoir analysis system as an alternative to traditional open-hole log analysis was tested as a method to reduce drilling rig time. On a series of five wells in the Gulf of Thailand, an integrated pulsed-neutron system that measures Sigma, inelastic spectroscopy, neutron porosity and density was used to drive the cased-hole analysis. The capabilities and accuracy of the cased-hole results were compared to open-hole porosities and water saturations. One concern for cased-hole logging is accuracy in this well-completion environment. These wells are completed as monobores with 2 7/8-inch tubing cemented directly into the 6 1/8-inch open hole (no well casing). Initially, the pulsed-neutron porosity coefficients for 5 1/2-inch casing were used with reasonable accuracy. To increase the porosity accuracy, the data from this test served as input to an artificial neural network for determining porosity coefficients in this specific borehole environment. The project consisted of 12,099 feet of log data including 30 gas sands, 5 oil sands, and numerous water sands in the five wells. The results of this assessment are shown via log examples over specific intervals. In addition, several cross-plots comparing open-hole data to cased-holed data show the results of this evaluation. Graphs of net pay, net effective porosity, net shale volume, and water saturation are shown for the entire project. Introduction Figure 1 is a map of fields in the Gulf of Thailand. Production from the fields operated by Unocal is approximately 1 BCFD of natural gas1 and 33,000 BPD of condensate.2 Since these reservoirs are highly compartmentalized and have limited drainage, it is critical for well-construction costs to be minimized. One technique that is appropriate for this reservoir environment is to drill slim wellbores and complete as monobores with 2 7/8-inch tubing cemented in open hole (no well casing). To reduce drilling-rig time and lost tool liabilities, a test of the capabilities of a cased-reservoir analysis system was devised. Five wells logged with a standard open-hole "triple combo" were selected to run the Computalog PND™ pulsed-neutron system. In a single logging pass this system measures Sigma, C/O ratio, neutron porosity and density. In this assessment the cased-hole porosities were of prime importance, and the cased-hole gas and oil saturation measurements were of secondary importance. These reservoirs are predominantly non-marine fluvial sands with interbedded shales and occasional coals. The logged intervals consisted of two different geometries: the upper sections are 8 1/2-inch boreholes with 7-inch casing and 2 7/8-inch tubing (casing-borehole and tubing-casing annuli cemented), the lower sections are 6 1/8-inch boreholes with 2 7/8-inch tubing centralized and cemented. Reservoir fluids are oil, hydrocarbon gas with carbon dioxide, and fresh waters (>5Kppm NaCl). The study was restricted to the shallow part of the productive section by the maximum temperature specification for the PND™ of 300F. At the studied depths (true vertical depth from -3500 to -6190 feet) the reservoir sequences have a low percentage of carbon dioxide (typical >10%). The low salinity of the formation water means Sigma will have poor oil-to-water resolution. However, the low cross-section of gas can be exploited to make a gas saturation calculation. The Sigma measurement is fairly borehole- independent and standard water saturation evaluations were done using the variable matrix model.3 The Carbon/Oxygen saturation measurement is very borehole-dependent, and characterization for this wellbore environment is discussed in the Results: Saturation from C/O section. Characterization of the porosity measurements is discussed in the following section.

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Accurate Oil Saturation Determination and Monitoring in a Heavy Oil Reservoir

Cited by 3 publications

References 0 publications

Tecnicas geoestatisticas aplicadas na modelagem da saturação de oleo

Tecnicas geoestatisticas aplicadas na modelagem da saturação de oleo

Is Accurate Gas/Steam Determination Behind Pipe Feasible with Pulsed Neutron Measurements?

Assessing the Capabilities of a Cased-Hole Reservoir Analysis System in the Gulf of Thailand

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