Analysis Of Water Injection Feasibility Of Chang 7 Reservoir Group In No.2 Oil Field Baizhuang Area

Baizhuang region is located in the south of the Yishan slope, which the main producing oil stratums are Chang6 and Chang 7 formation. The pilot test area has been set up in Y2#-Y59# well block in Chang 7 reservoir but achieved a little. The current productive rate is 0.1m3/d, therefore it is necessary to find a new block to do the pilot test in this area. So far the pilot test area, which is to say the Y2#-Y59# well block has relatively large different in production rate of single well and the water content. The daily average production per well is high in the first week, but the production plateau is short and the nature decline is rapid. As a consequence, it has a negative impact on the sustainable development of oilfield. In order to solve these problems and enhance the production as well as recovery efficiency, it is essential that to study whether the Chang 7 reservoir is suitable to have the water flooding process.This paper has provided the solutions of the study area through the research of the geological conditions. This study was based on multidisciplinary theories like the reservoir geology, the sedimentology, the petroleum geology and so on. Comprehensive methods like mathematical statistics, data analysis and field observation are combined with related analysis test to evaluate the flooding effect, it has also given the geological basis for the setup of the new advanced water flooding experimental area.The Chang 71 and Chang 72 reservoir of Baizhuang region developed the underwater distributary channel and interdistributary bay microfacies of delta front subfacies. The sands of underwater distributary channel were cut by the interdistributary bay which can have a great effect of waterflooding. Normally the waterflooding area was selected in the place where the connectivity of the sand is good. The interdistributary bay area should be avoided in waterflooding. The sand of the underwater distributary channel basically distributes as band and reticular shape, the range of the width of the channel is from 1.2m to 2.0m, the waterflooding effect is bad. Besides, since the channel sand bodies were separate by interdistributary bay mud and the thickness of individual sand body is thin, the region is not suitable for the injection.Though the analysis data such as scanning electron microscope, the mercury, the physical properties, the five sensitive experiment studies and the compatibility, it is considered that the illite has caused the block of the pores. At the same time, the mercury injection curves have shown that the pore-throat type of the Chang 7 reservoir is microporous-fine throat, the capillary pressure is small, the displacement pressure and the the ejection saturation is low. The poor physical properties led to a bad effect of waterflooding.There are a large number of argillaceous interlayers and the intercalated bed in the study area, the frequency of the interlayer is higher compared with the adjacent area. Additionally, the thickness of layer is over 1m. The interlayer is easily to break when waterflooding which bring adverse effect in the waterflooding. Moreover, the poor connectivity of the reservoir in this area also has a disadvantageous influence for the water injection.To sum up, it is considered that the reason of the low efficiency of waterflooding is complex based on the geological conditions. It mainly perform at the flowing aspect, the physical properties of the reservoir is poor, the reserve is insufficient, the reservoir is non-Darcy flow, threshold pressure gradient is high, the natural productivity is low, injected water flows along the fractures, severe watered-out, poor cementing quality, channeling effect is serious.It is believed that the research area does not possess capacity of water injection on a large scale on the basis of the geological evaluation. The new waterflooding area should be considered according to the tectonic structure, sandbody connectivity, sedimentary, reservoir property, oil source condition and the field oil test data. The two new water injection ploit areas were selected which are Y 64# to Y87# block and Y67# to Y84# block. The distributions of the Y67# to Y84# wells have been optimized. The disposition number of the wells are 25,4 drilled wells are used and 21 new wells should be drilled. The water injection well and producing well ratio is 1:3.1.The distributions of the Y 64# to Y87# wells have been optimized. The disposition number of the wells are 12,2 drilled wells are used and 10 new wells should be drilled.