Study On Designing Treatment Of Proifle Control And Decision-Making Technique

Bohai oilfield is characterized by thick layer, high permeability, serious heterogeneity, low cementing strength of rocks and high viscosity, etc. During water flooding process, the injected water mainly enters into high permeability layers. And the low and medium permeability layers are bypassed. As oil saturations of high permeability layers decrease, pore structure have been damaged, and "water fingering" and "water breakthrough" appear, reservoir heterogeneity is more serious, causing to inefficient or ineffective circulation of water in high permeability layers and seriously affecting development effect. In view of unique production process conditions and characteristics of reservoir at offshore oilfield, the conventional methods have been unable to meet the needs of offshore oil field. Deep profile control technology has been a more effective measure in recent years which has been applied successfully in some dometic fields. Practice showed that the deep profile control technique can effectively avoid water to enter into the high permeability layers, stabilizing oil production by water control. In order to scientifically, timely and reasonably make the profile control plans and to obtain better measures effect, profile modification is predicted firstly and then designed. At present, the long study period, the incomplete or inaccurate data, and mathematical diffculties can afftect the predition result. Based on core flooding test data and results of NB35-2, Lvda, Chengbei, and Zhanjiang oilfields, incremental oil effects and its influencing factors were analyzed. Furthermore, based on BP neural network, the model was established and the profile modification was predicted. The experimental data of physical simulation were taken as the sample for network, which resolved the difficulties caused by lacking of field data. On this basis, according to the actual demand of Bohai oilfield profile modification design, the methods of well and layer selection and effect prediction methods were researched, and the technique of decision and effect prediction analysis used in the computer system were developed. In the oilfield, in accordance with decision system in the well and layer selection function module, A21, B17and A24three wells were needed to implement profile modification. According to the indoor evaluation results, the concentration of "low molecular weight" polymer manufactured by PetroChina Daqing Refining Company,"polymer:Cr3+=180:1" polymer gel was recommended. In the process of optimal design, taking a well (A21well) for example, it turned out to be the average injection concentration was3500mg/L and slug size was0.13PV. According to practice, the decision-making system was characterized by reliable theory, reasonable software structure, and convenient input and output, etc. At last, it can meet the need of the BoHai oil field, and provide a new incremental oil production prediction method for oil fields.