Exploration and Practice of Integrated Re-fracturing Technology for Horizontal Wells in Ultra-low Permeability Reservoirs in Huaqing Oilfield

Abstract

AbstractThe Huaqing Chang 6 reservoir in the Ordos Basin is a typical ultra-low permeability reservoir, in the early stage, horizontal well staged fracturing and water injection was used to supplement energy development. Affected by factors such as tight reservoir low pressure and difficulty in establishing long-term injection-production displacement, long-term production of horizontal wells has a large decline in output, and the oil recovery rate and cumulative recovery are low. In this paper, the numerical simulation method is used to study the distribution of remaining oil, pressure field and dynamic in-situ stress field of horizontal wells, established a horizontal well repeated fracturing comprehensive well selection index method covering three factors of reservoir, completion and production to achieve potential well sequencing, forming the original fracture “four-step method” and secondary reform sweet spot classification and classification evaluation method to achieve potential section Preferred. For the purpose of expanding the volume of reservoir reconstruction, enhancing formation energy, and improving oil-water replacement efficiency, the research has formed an integrated design model of horizontal well pressure flooding and repeated reformation technology that integrates “volume transformation, energy supplementation, and imbibition flooding”. Repeated reconstruction process of mechanically packed volume fracturing and supporting construction string. Mine field test analysis shows that the SRV (reservoir reformation volume) of the integrated repeated fracturing of horizontal wells is more than twice that of the initial conventional fracturing, the FCI (fracture complexity index) is increased by 0.1–0.2 compared with the conventional fracturing, and the formation pressure retention level is increased from 75% before recompression To 120%. More than 10 horizontal well exploration tests were carried out in the representative Y284 Chang 6 ultra-low permeability oil reservoir, control blasting production after refracturing, average oil production per well has been increased from 2 tons to 10–15 tons per day. The spontaneous injection period has reached more than three months. After one year of production, the average production is still 10 tons per day, and the cumulative oil increase of a single well exceeds 2500 tons, the oil recovery rate will be increased from 0.22% to 1.05%, the EUR (predicted final cumulative oil production) can be increased from 12,000 tons to 25,000 tons, the final output-to-input ratio of economic benefit evaluation is greater than 1.2, and the internal rate of return is greater than 8%. This technology provides a reference for other low-permeability and tight reservoirs and low-yield horizontal wells to greatly increase single-well production and final recovery, and to improve reservoir development effects.KeywordsLow permeability tight reservoirHuaqing oilfieldLow production horizontal wellIntegrated refracturingVolume fracturingEnergy supplementationImbibition flooding