Abstract:

The shale gas fields in Southern Sichuan are developed in an integration mode of testing, production and transmission, which has realized the development goals of cost reduction, emission reduction, fast production commissioning and early returns. However, a lot of empirical practices serve as reference of decision-making during implementation of integration practices. There is a lack of general guidance. In order to study the post-frac soaking, the flowback system and the drainage measures, the experiments of overpressured NMR imbibition, permeability stress sensitivity and gas-liquid two phase percolation are conducted, the flow regime and the distribution of pressure profile are simulated, and the discharge and production effect of more than 30 wells in Southern Sichuan shale gas field has been evaluated. The results show that the entry of fracturing fluids into reservoir through imbibition is beneficial to increasing the complexity of shale cracks, and the optimal shut-in time of Southern Sichuan shale gas field is 4~10 days. Meanwhile, a six-staged flowback system is formed, and a post-frac drainage guide chart is established. It is determined that tubing and manual lifting should be implemented when the flow regime changes and the tube should be installed at the well deviation of 70° ~ 85°. Besides, the drainage strategy is also proposed. In general, the research results are of great significance for guiding post-frac production control and drainage technology.

Key words: deep shale gas, NMR, stress sensitivity, wellbore flow regime, drainage technology, tubing design