Optimization of horizontal well injection-production parameters for ultra-low permeable–tight oil production: A case from Changqing Oilfield, Ordos Basin, NW China

Abstract

There are two kinds of displacement mechanisms and three different seepage stages during horizontal well development process with water injection energy. A reasonable injection-production working system of the basic principles and parameters are determined according to the evaluation results of horizontal well development test on the basis of understanding fundamental rules. (1) Advanced water injection energy supplement mode is proposed with the combination of injection wells and large volume water fracturing of horizontal wells. (2) Theoretical calculation chart of directional well advanced water injection and water injection intensity is established for various reservoirs. (3) The timing of advanced water injection should follow the completion of the horizontal wells. (4) Reasonable initial production of horizontal well is determined by the relationship of remaining fluid volume with row spacing, advanced injection water volume and flood front advancing velocity. (5) Reasonable production flowing pressure is slightly greater than saturation pressure before water injection does not work, when it works, the reasonable production flow pressure maintains no less than two-thirds of saturation pressure, and adjust it timely combining with dynamic production. Based on the research results, the HQ oilfield put 80 horizontal wells into production during 2013, the proportion of water-breakthrough wells reduces from 8.8% to 3.0%, the annual decrease of the average production of single horizontal well is controlled within 15%. Key words: ultra-low permeable–tight oil, horizontal well, volumetric fracturing, remained underground fluid, injection-production parameters optimization, Changqing Oilfiled