Research On Improving Development Effect Technology Of Fu Yu Oilfield In High Water Cut Stage

Fuyu oilfield is located in the east edge of the central depression area of the southern Songliao basin. Since 1959, the oilfield has entered the stage of high water-cut after 50 years development, and there are three big problems during the exploitation process. The first problem is inefficient water circulation. To prevent this, for now the main method is based on mechanical water plugging technology, which can only plug perforation holes of the wellbore. However, the improvement of the contradiction in plane is limited. Besides, it is difficult to release plugging. So a new water plugging method needs to be researched. Another problem is that there are normally multiple layers available while the difference between the layers is predomminant. Commingled production does not match with water injection. Layered oil production theory and supporting technology need to be researched. The next problem is that in Fuyu oilfield, mudstone interaction exists, artificial and natural fracture is developed, and water breakthrough occurs easily after fracturing construction. Therefore, artificial change of fracture orientation is needed to reach optimization of reconstruction effect. To solve the problems above mentioned, with the combination of theoretical analysis, numerical calculation and indoor physical simulation methods, the development effect mechanism and technique for separate-layer plugging which can avoid clearing jams, separate-layer oil production with double flowing pressure pump and oriented perforating fracture have been researched. The results are listed as follows:1. The mathematical model of cement slurry flow has been established based on columnar diffusion behavior. The flow behavior of cement slurry through cores is simulated. The relationship between the diffusion rate and the diffusion distance of cement slurry, under different injection pressure and permeability, is given. The injection pressure of cement slurry for reservoirs with different permeability is also investigated.2. Through indoor experiment of cement slurry plugging, we got the following conclusions. The pure cement grout loses liquidity basically when its plugging radius reaches 1.5m. By screening, the cement slurry formulation with Class G cement+0.02% retarding agent +0.2% drag reduction agent+0.2% filtrate reducer+44.0% water will increase plugging radius longer than 10m; the core sample plugging ratio of G cement over 96% can meet the requirements of the industry. For low permeability cores low density cement slurry should be chosen, which will allow the slurry go into the small pores and improve the blocking ratio; The thickening time of the slurry is determined by the amount of additives. However, when the final thickening time is over 36 h, the plugging can meet requirements.3. The injection cement technique pipe with double deblockings which can prevent being stuck is researched. It can avoid clearing jams when plugging, meet the injection technical requirements and guarantee the security construction of layered cement water plugging. Besides, it realizes that there is no cement plug in wellbore after cement plugg is in place. Moreover, it reduces construction costs, improves construction efficiency and provides technical support for the layered cement plugging technique.4. Multiple layers IPR model for separate and commingled production is established, and the interference of high-pressure layer on low pressure layer and back flow phenomena is considered comprehensively. Meanwhile the relationship between pressure difference of dynamic fluid column and pressure difference of different layers is considered. Then the IPR model for separate and commingled production established in this paper can provide flowing pressure calculation method for separate production with double flowing pressure.5. The separate production technology with double flowing pressure is designed, which applies a single pump to release separate production. The technology is easy to implement, the cost is low and workover is not frequent. The upper and lower layers can both produce at their reasonable pressure, and pumps can be linked to any position, which solves the serious interference when layers product together in Fuyu oil field which influence the well production potential.6. Based on the extended finite element theory, the mathematical model of fractures start to crack and develop under the condition of oriented perforation is established, and the extended finite element numerical model is formed. A wide range of numerical simulation is conducted based on this model. Then the influence of the perforation azimuth and horizontal principal stress difference on the fracture extension and diversion is researched, and the corresponding charts are established.7. The direction of fracture initiation can be changed artificially through oriented perforation, by cooperating with the stress difference at principal stress direction and the horizontal principal stress direction to select the appropriate perforation azimuth, and control the fracture extension direction artificially. As a result, the reservoir reconstruction effect can be improved.8. On the basis of established technology limits of separate layer plugging which can avoid clearing jams,separate layer production at double flow pressure with single pump and oriented perforation fracturing technology for plugging to choose well and layer. The following wells in block West 10-2 are selected. The wells including 6 cement plugging water wells, 4 separate-layer producing wells of double flow pressure with single pump, 4 oriented perforation fracturing wells. Then, four sets of numerical simulation method are established. As the prediction results show, after water plugging, separate-layer producing and fracture, the decline rate of annual production in 2015 is 2.0%, is 5.5% lower than the measures are not taken.