温度对多类型超深层碳酸盐岩气藏渗流能力的影响

Effects of temperature on seepage capacity for a multi-type ultra-deep carbonate gas reservoir

超深层碳酸盐岩气藏埋藏深、温度高,高温对多类型储层渗流能力的变化规律尚不明确。选取高石梯—磨溪区块灯四段气藏储层岩心,通过测定升温和降温过程中岩样的气体单相渗透率和不同温度下的气水界面张力及气水两相相对渗透率,得到温度对多类型超深层碳酸盐岩气藏渗流能力的影响规律。研究结果表明:在20~120℃范围内,随温度改变,不同类型储层岩样气体单相渗流能力均呈幂函数变化,升温过程中气相渗透率下降受气体黏度升高、白云石晶体膨胀及岩石颗粒脆化后运移的共同影响,一次升温和降温后,缝洞型岩样由于微裂缝发育渗透率不可逆程度最高为82.52%,孔隙型岩样由于小孔喉发育次之为27.63%,孔洞型岩样最低为9.46%,缝洞型岩样为温敏型岩样,孔隙型和孔洞型岩样为耐温型岩样,多类型气藏的温度上限集中在44~50℃附近;温度升高主要通过降低水气黏度比来提高气驱水效率和气水两相渗流能力,地层温度下的水气黏度约为常温条件下的1/3,高温条件下多类型储层的气水相渗曲线更能代表实际地层的两相渗流特征。温度对多类型超深层碳酸盐岩气藏渗流能力的影响规律可为此类气藏的高效开发提供理论依据。

Ultra-deep carbonate gas reservoirs are deeply buried and high in temperature, and the change rule of high temperature on the seepage capacity of multi-type reservoirs is still unclear. The cores of the fourth member of Dengying Formation in the Gaoshiti-Moxi area were selected, the gas single-phase permeability of the rock samples during the heating and cooling process, the gas-water interfacial tension and the gas-water two-phase relative permeability at different temperatures were measured, and then the effect law of temperature on the seepage capacity of the multi-type ultra-deep carbonate gas reservoir was obtained. The research results show that: in the range of 20-120 ℃, with the change of temperature, the gas single-phase seepage capacity of different types of reservoir rock samples changes as a power function. The decrease of gas-phase permeability during the heating process is jointly affected by the increase of gas viscosity, the expansion of dolomite crystals, and the migration of rock particles after embrittlement. After one heating and cooling process, the irreversible degree of permeability of fractured-cavity type rock samples was the highest at 82.52% due to the development of micro-fractures, followed by 27.63% for pore type due to the development of small pores and throats, and the lowest was 9.46% for pore-cavity type. Fractured-cavity rock samples are temperature-sensitive rock samples,while pore type and pore-cavity type rock samples are temperature-resistant rock samples. The upper temperature limit of the target multi-type gas reservoir is concentrated around 46-50 ℃. The temperature increase mainly improves the gas-displacing water efficiency and the gas-water two-phase seepage capacity by reducing the water-gas viscosity ratio and the water-gas viscosity ratio at the formation temperature is about 1/3 of the normal temperature. The gas-water phase permeability curves of multi-type reservoirs under high temperature conditions can better represent the two-phase seepage characteristics of actual formations. The effect law of temperature on the seepage capacity of multi-type ultra-deep carbonate gas reservoirs can provide a theoretical basis for the efficient development of such gas reservoirs.