关键词: 高温高盐油藏, 水驱剖面, 调剖实验, 诱导盐沉析技术, 三维物理模拟

Abstract:

The reservoirs of an oilfield in West China have the characteristics of high temperature (123℃), deep bury (4880m), high salinity (18.1×10⁴mg/L) and high pressure. The alcohol-induced salt precipitation technology was adopted to control the profile of the reservoirs for enlarging the sweep efficiency and enhancing oil recovery. The massive experiments were performed to pick up the excellent injection system by means of two parameters, including the salt precipitation quantity and unit crystal quantity. The microscopic structure of crystal grain, distribution of grain size, distribution of pressure and the situation of enhanced oil recovery were analyzed by means of SEM, grain size analysis units and three-dimensional physical simulation. The experimental results indicated that under the same volume ratios of inducing agent and salt solution, the inducing agents arranged according to their induction ability from big to small as follows: alcohol-A, alcohol-B, acid-2, acid-1 and amine-X. The investigation showed that the salt grains with the form of consecutive distribution could be precipitated from solution. The average grain diameter of the salt grains is 63.645μm. In the vertical heterogeneous reservoir, the alcohol-induced salt grain could elevate the fluid flow resistance, increase the injection pressure and change the flow direction. In the lateral direction, follow-up water could flow from the mainstream line to the remaining-oil region to displace the remaining oil and enhance the plane sweep efficiency. In the vertical direction, follow-up water diverted from the high-permeability layer to the low-permeability layer to enhance the vertical sweep efficiency. The experimental data indicated that oil recovery was increased to 62.8% and was elevated by 27% comparing with the first water flooding after injecting 0.5PV inducing agent and 1.5PV follow-up water.

Key words: high-temperature and high-salinity reservoir, water-flooding profile, profile control experiment, salt-induced precipitation technology, three-dimensional physical simulation