Abstract:

The JS₂² gas reservoir in the Xinchang Gas Field is the microfacies of distributary channel deposit in the delta front subfacies. The mudstone interlayer developed in some sandstone layers form the channel sediments twice. For some gas wells with double developed sand layers, the perforation and fracturing are carried out only in one of the two layers, while the rest may be blocked by mudstone interlayer, resulting in its untapped situation. However, the understanding of the distribution rule of the mudstone interlayer is unclear, and the sealing performance of interlayers hasn't been verified by precedent, limiting the development of the remaining gas in this reservoir. By the establishment of the logging curve identification standards of the interlayer, the interlayer of every single well is identified and divided, and the development scale and plane distribution rule of the interlayer are studied. And then, the old wells are used to explore the vertical sealing performance of the mudstone interlayer inside the channel sandstone. The study results show that the mudstone interlayer, with the thickness of 1~15 meters, is mainly distributed in the east of the JS₂² gas reservoir, and has the characteristic of one thin-line area laying between two thick areas along the distribution direction. In the application of potential tapping of Well-A1, the production obviously increase after the perforation and sand-fracture, firstly verifying that the mudstone interlayer with the thickness of 10 meters in A1 well area has better vertical sealing performance. This achievement will provide new ideas and practical basis for the development of remaining gas in the JS₂² gas reservoir, and is of great significance for improving the recovery rate of the entire gas reservoir.

Key words: Xinchang Gas Field, JS₂² gas reservoir, interlayer, remaining gas, potential tapping of old wells