【正文】 ed for them. Microbial Enhanced Oil Recovery (MEOR) technology is considered promising for fault block oil reservoirs, whose related research was not launched until 1990s in Shengli Oil Field by a specialized team engaged in research and test in MEOR. Once their purpose was to select the bacteria type, suitable for the reservoir environment and capable to enhance the oil displacement efficiently, which was first ground cultured then injected into the reservoirs. At the beginning of this century, research revealed indigenous bacteria in reservoirs are very active, so the research focus shifted to indigenous bacteria enhanced oil recovery. Currently, oil reservoirs have been considered as an ecosystem into which material such as specific microbial formulation, inorganic or organic nutrient and air have been injected to regulate them: the microbial munity structure and function inside might change, increasing the bacteria density, producing biosurfactant and improving the oilwash efficiency through in situ breeding. Based on research in the laboratory, a MEOR field test has been carried out in Block Luo801 in Shengli Oil Field since 1999. The test method has been adjusted twice in the 10 year period in the hope of exploring the potential of MEOR technology to improve oil recovery in fault block oil reservoirs. 2. Test Area Reservoir Geology Block Luo801 is a small block in Shengli Oil Field, a lithologic structural reservoir with a temperature ranging from 75 ℃ to 80 ℃. It is open in the north and the southern part is closed by an eastwest arc fault, where the test area is located on the hanging wall. The area bearing oil is ?? km2 with the crude oil reserves 291 104 t. The reservoir depth is from 1680 m to 1800 m and the original formation pressure is MPa. The oil pool of the test area is located on the West Wing of the noselike structure, whose strata are high in the south and low in the north with an angle ranging from 5186。Figure 3 Actual production and decline forecast curves of Luo 801 Development Effect Improvement1) Slow the natural declineAfter the implementation of MEOR, the production decline has slowed down significantly in Luo801 with the highest natural decline rate from 32% to % in 2005. Though production has an overall downward trend, the average decline rate is far lower than that before flooding recovery ( Figure 4). Figure 4 Production decline curve of the test area 2) Enhance oil recoveryAfter the implementation of flooding and MEOR, the situation has been improved in Luo801. The recovery rate rises obviously, which was % based on Flooding Dynamic Calibration, increasing by % over the one calculated with the empirical formula of Shengli Oilfield, %. If the MEOR operation goes on under the current conditions, the ultimate oil recovery rate is expected to increase by % to achieve extra recoverable reserves 180。103mm2, and the ground oil viscosity , formation water type NaHCO3 and TDS 7795 mg/L. Test area reservoir parameters are shown in Table 1 and the wells’ position is shown in Figure 1. Table 1 MEOR test area reservoir parameters of Luo801ItemDataItemDataOil bearing area（km2）Formation water TDS mg/L9794Reserves（104t）291Formation water typeNaHCO3Reservoir typelithologicstructuralOriginal oil and gas ratio30Reservoir depth (m)16801800Original formation pressure (MPa)Porosity（%）Saturation pressure (MPa)Air permeability（103um2）218Formation saturation pressure difference (MPa)Oil saturatio