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The New Method of the Sweet Spot Discrimination and Predictive Production in North American Shale Oil

Abstract

The cost of horizontal drilling and hydraulic fracturing in shale oil and gas development is very high. In order to improve economic benefits, the research on sweet spot discrimination need to be carried out immediately. This paper first analyzed that the main factors of sweet spot in North American shale included total organic carbon content, rock brittleness, porosity and fracture. Then rock physics analysis was the key of sweet spot discrimination, while the quantitative logging interpretation of reservoir parameter is the basis of rock physics. For the logging quantitative evaluation problem in North American shale, a kerogen-corrected logging model has been used, and the core technology and flowchart of reservoir quantitative evaluation in shale oil and gas based on elemental capture spectroscopy logging have been built. The interpretation results in block A and block B in North America are of high precision by using the new evaluation method of logging. On the basis of logging interpretation result, rock physics analysis has been carried out, and the results showed that the porosity was the key factor of affecting yield in block A. Because P-wave impedance can characterize porosity effectively, the technology combination of prostack inversion and fracture analysis is used to predict sweet spot of shale in block A. The result was used to guide drilling deployment and fracturing design, and shale oil and gas yield is greatly improved. The total organic carbon content and rock brittleness are the key factors of shale oil and gas production in block B. So prestack simultaneous inversion technique was used to solve the problem of sweet spot discrimination in block B. Drilling results confirmed that the shale oil and gas yield in sweet spot region was very high. Thus rock physics is the core and key of sweet spot discrimination.