Key Technology and Application of Thin-Bedded Tight Sandstone Gas Reservoir in Horizontal Well Development

The gas host intervals of the eighth member, Permian Shihezi Formation, in the Sulige gas field are characterized by a thin strata thickness, low porosity and permeability, and high heterogeneity, resulting in poor continuity and connectivity of the sandstone bodies. These collectively lead to a low vertical well production rate, a challenge that needs to be improved imperatively. Here, technical options are studied and innovated in the horizontal pilot development, seeking for a solution package including horizontal well development, design, geo-steering, rapid drilling, and fracturing treatment to improve individual well production rate. The application of this solution package has successfully guided the deployment of the well location, optimized the well track, and increased the individual well production rate. In 2016, the horizontal wells had reached the number of 59, the average length of horizontal interval is 1211 m, the actual average sand ratio drilled along horizontal well is 60.2%, and the average open-flow capacity is 4.87 million m3 per day, three times more than the vertical wells. When we talk about tight sandstone gas reservoir, it is of variety definitions. According to The Federal Energy Regulatory of the United State, it is defined as the in situ permeabilities to gas are generally less than 0.1 millidarcy (md) and porosity ranges from 3 to 12%. This has been the most widely popularized definition. Experimental data of the Sulige gas field suggest that the permeabilities of the regular conditions are about 10 times more than those in situ, indicating a tight gas reservoir. It has been found that the development of the horizontal well is facing the problem of low effective thickness and small single sandbody. Efforts will be concentrated on tackling the key technology such as horizontal well development, horizontal well design, geo-steering, rapid drilling, and fracturing treatment to improve the individual well production rate.