TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe chemical screening and chemical formulation studies were discussed in this paper, and the pilot test results as well for the ASP combination flooding pilot test in Karamay EZ District. Also the designing strategies of the ASP process were included in this paper. The ASP pilot test started from August 21,1995 with the beginning of NaCl brine pre-flush in order to condition the reservoir, then followed by ASP slug and Polymer slug. The post-water injection was applied after the designed chemical injections. The 24%OOIP incremental oil recovery was achieved in the whole test area with about 25%OOIP incremental oil recovery for the central production well . 5 Conclusions1. The laboratory studies showed that the EZ District in Karamay Oil Field was suitable for ASP flooding technique in technical point of views. 2. The synergistic effect was observed for KPS/ Na 2 CO 3 system with pilot area crude oil. 3. The surfactant, KPS-1, manufactured in local refinery was very compatible with reservoir fluids and rock of the target pilot test area. 4. Both ultra-low IFT and proper mobility control were very important for improving oil recovery purposes for most of Karamay reservoirs, the highly heterogeneous conglomerate reservoirs, 5. The implement of the ASP process improved both planar conductivity and vertical flow in the pilot test area. 6. The 24% OOIP incremental oil recovery for pilot area and 25% OOIP incremental oil recovery for the central production well were achieved by the use of ASP combination flooding process in pilot test area.

XinJiang oilfield is located in the Northwest of China, in which large oil reserves have been discovered in reservoirs with very low permeability (<14×10 -3 μm 2 ). These reservoirs are featured with light oil in moderate depth, high reservoir pressure, but relatively low reservoir temperature (65~78 o C) and low oil viscosity (<10mPa•s). Primary production and limited water flooding experience have shown that the recovery factor in these reservoirs is very low due to lack of reservoir energy and poor water injectivity. Gas injection has been optioned as an alternative secondary or tertiary technique to maintain reservoir pressure and/or increase sweeping and displacement efficiency. In this study, the feasibility of air injection via a low temperature oxidation (LTO) process has been studied. Laboratory experiments were focused on LTO characteristics of oil samples at low temperature range and core flooding using air at various reservoir conditions. Reservoir simulation studies were conducted in order to predict the reservoir performance under the air injection scheme and to optimize the operational parameters. The oxygen consumption rates at reservoir temperature and IOR potentials at different reservoir conditions were assessed for a number of selected reservoirs in the region. A pilot project has been designed based on experimental data, reservoir simulation results and field experience of air injection gained in other regions of China. Issues related to safety and corrosion control during air injection and the project economics were also addressed in the paper.

Taking the conglomerate from Xinjiang Oilfield as study object, the porosity distribution characteristics of the conglomerate were analyzed with CT scanning; through the online monitoring of the water and polymer flooding process in a conglomerate core using an CT scanning system, the saturation profile along the core and the CT reconstructed images of core section during the displacing process were obtained; oil displacement mechanism was analyzed according to a new characterization parameter, "oil saturation frequency distribution". The results show that the conglomerate has strong heterogeneity, resulting in "dominant channels", and in turn ineffective water circulation and low water flooding oil recovery, moreover, the oil in high oil saturation area is produced first. In polymer flooding, the oil in high and medium oil saturation areas can be produced but the oil in low oil saturation areas still cannot be produced. Oil produced in the subsequent water flooding is still mainly from the high oil saturation areas. For conglomerate reservoirs, previous water flooding should reach as high water cut as possible so as to strengthen the slug effect of the polymer. Meanwhile the injection volume of polymer should be reduced, and a subsequent water flooding should be used to push the polymer slug to produce oil.

In the northern part of Erzhong District in Karamay conglomerate oilfield, Xinjiang, China, ASP pilot tests have been conducted in 13 wells in a pilot area of 0.031 square kilometers since September 1994. The pilot area was developed through combining laboratory results in recent years with specific conditions in the field. This test is aimed to verify oil displacement efficiency of ASP and related reservoir behaviors, to improve production techniques necessary to obtain remaining oil from conglomerate reservoirs, and to provide data for economic feasibility evaluation. P. 385

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