| Bottom water coning is one of the biggest problem to exploit the bottom water reservoir. Water cut increases greatly with water breakthrough, which leads to the well shut down. There are many disadvantages in the developing of the bottom water reservoir with the selective completion. Water plugging can be carried out in the Water production interval under the selective completion which has been proved an effective completion method to increase water free production period and cumulative water free production rate. For this, segregated optimization theory is studied in this paper, which is on the based of new selective completion with external casing packer and blank tubing that is different from conventional selective completion with ECP. So the selective completion can increase water free production period by means of increasing the length of blind tube. This paper studies the key technologies for selective completion of system theory, provided relevant theoretical basis for the development of oil and gas reservoir development.First, based on the theory of fluid mechanics in porous medium, engineering mechanics and reservoir engineering, a coupling productivity model of selective completion and a three dimensional model of water buildup have been established by mathematical and physical methods. Considering the elements such as anisotropy, filtering interference, conduit flow drawdown as well as damage zone caused by drilling and/or completion, a full set of loop iteration solving schemes for the stable coupling model have been established by means of discretized semi-analytic method, relevant theories such as permeation fluid mechanics, engineering fluid mechanics, reservoir engineering and mathematics. Then, with the help of computer programs, which are compiled on the base of the scheme mentioned above, rate, flowing pressure, breakthrough time and lifting height distribution profiles have been worked out. According to the results, selective completion optimization is obtained, which is on the based of cumulative free water production rate and stimulation ratio as objective function. Segregated optimization includes open degree, the number of open segment and blind tube position. Then the best completion parameter is recommended.Second, on the basis of the coupling productivity model and three dimensional bottom water creating model, sensitivity analysis of productivity, water cresting process and cumulative free water production rate was done. For homogeneous reservoir, dynamic segregated and pre-segmented optimization is proposed. For heterogeneous reservoir, because of heterogeneity of penetration, the position of bottom water breakthrough is randomness. Based on the plane heterogeneity of penetration, the segregated optimization of is proposed according to the level of permeability. Third, the result show that using dynamic segregated to increase cumulative free water production rate is very significant. However, the existing technology disable guarantee the validity of it. So pre-segmented technology is more appropriate in oil reservoir development. Using pre-segmented technology to increase stimulation ratio is very significant in homogeneous reservoir and heterogeneous reservoir, especially to heterogeneous reservoir. Horizontal well can delay bottom water cresting to a certain extent in the bottom water reservoir, however, premature water breakthrough in the horizontal well.So selective completion technology can effectively delay of bottom water coning in the bottom water reservoir. Applying the results of this paper, segregated optimization including open degree, the number of open segment and blind tube position is designed. So it can effectively delay water coning and maximize the cumulative free water production rate.This paper studies the key technologies for moderate selective completion of system theory, appropriate for the the bottom water reservoir development provided relevant basis theoretical, which has important theoretical and practical value. |
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