Application of the composite gas production technology to tight sandstone gas reservoirs: Negative-pressure production and foam-assisted dewatering

To improve the drainage performance of the low-pressure low-rate wells with co-production of gas and water in the Sulige tight sandstone gas reservoir, the composite gas production technology of negative-pressure production and foam-assisted dewatering was developed. The applicability of the composite production technology was analyzed in accordance with the gas production of wells per unit drawdown pressure, remaining recoverable reserves in the low-pressure low-rate production stage and production system nodal analysis of the representative Sulige block. Moreover, the well candidate criteria were proposed for the composite production technology, considering the applicability analysis, production stimulation mechanisms and key parameters of the negative-pressure production equipment, and field testing was performed in three wells selected correspondingly. The results showed that the presented technology is highly applicable to gas wells that can no maintain normal commingled flow of water and gas in the case of low pressure and low production rates. As the tubing pressure at the wellhead drops to zero, normal mixed flow of water and gas can be maintained even with the gas production of about 0.2×10⁴ m³/d. The quit-flowing pressure can be further lowered, with the help of foam-assisted dewatering. Three wells of Type-Ⅰ, Ⅱ and Ⅲ, respectively were selected for field testing. The average daily production gains were 0.50×10⁴ m³/d, 0.39×10⁴ m³/d and 0.28×10⁴ m³/d respectively during the testing, and the minimal wellhead tubing pressure reached −0.05 MPa. Hence, the composite production technology can effectively lower down wellhead pressure of gas wells and tap the gas production potential. Also, better performance of the presented production technology is expected in reservoirs with higher quality.