Abstract:

The main gas reservoirs in the Xinchang gas field in western Sichuan basin have entered the middle to late stage of development, and potential tapping of the existing wells is an important means to maintain the effective development of the gas field. As high-quality reservoirs are further recovered, the original criteria of candidate well selection for tapping potential are no longer applicable to the current development situation; instead, it is urgent to establish new criteria for well/layer selection aiming at recovering the hard-to-produce reserves. The potential tapping effect of typical wells in the Penglaizhen formation of Xinchang gas field was evaluated, and the reservoir quality and reserves recovery of the target interval were analyzed. Combining with the single-well production performance, the candidate well selection criteria suitable for the current development characteristics of the study area were established. The results show that the potential tapping effect is affected by multiple factors such as well logging, seismic response and adjacent well producing, which should be comprehensively considered to reduce the failure risk in potential tapping. When candidate wells are selected in the same favorable zone or the same fracture strike, the lower limit of well spacing to a neighbouring well is 350 m, and the upper limit of cumulative gas production from a single layer of a neighbouring well with the well spacing of 350 m is 0.20×10⁸ m³. Commingled production from multiple layers with secondary favorable microfacies is more applicable in the middle to late development stages, which is beneficial for the successful potential tapping.

Key words: Xinchang gas field, Penglaizhen formation, gas reservoir, potential tapping well, effect evaluation, candidate well selection criteria, late development stage, reservoir quality