For the fields of Uzbekistan, whose development is either complete or at the late stage, with gas deposits confined to terrigenous reservoirs, the gas recovery factor varies from 0.50 to 1.00 with an average of 0.64. Such a scatter allows us to conclude that some hydrocarbon reserves are underestimated, whereas others are overestimated. The gas recovery of terrigenous pay reservoirs developed in the natural (gas) mode depends mainly on the determination of hydrocarbons initially-in-place, field development system efficiency, lithological characteristics of the reservoirs, pore space structure peculiarities along the area and section of the pay horizons, their thickness persistence, and the homogeneity of their interlayers. Given these factors, we have examined the ultimate gas recovery of deposits across the Sudochy deflection fields (Republic of Karakalpakstan, West Uzbekistan). The reserves were estimated by the pressure-drop method, and the criteria were the volume of gas initially-in-place involved in drainage and how it changed during operation. Causes analysis for obtaining specific ultimate gas recovery values (g) allowed us to divide all the considered fields into four groups: А (g = 0.80–0.95); В (g = 0.70–0.80); С (g = 0.60–0.70); D (g = 0.50–0.60). The study results show that the forecast gas recovery factors are mainly close to those actually achieved, so they can be used to predict gas recovery factors of terrigenous reservoirs.
Keywords: GAS, GAS RECOVERY, RESERVOIR, TERRIGENOUS ROCKS, RESERVOIR PROPERTIES, DEPOSIT.