There are more than 80 horizontal wells with bottom water reservoir in Tarim Oilfield, China. Up to now, water breakthrough occurred to most of them and oil production declined severely. How to control the increasing water-cut in horizontal wells is one of the principal tasks at present. However, there are many factors affect the increase of watercut. Among which, the effect of pressure drawdown is most sensitive and elusive.
Using considerable practical production data and numerical simulation for horizontal wells, the production history match and prediction for the TZ402CIII reservoir behaviors were performed and subdivided into different watercut stages in this paper. Based on the numerical simulation results, the relation between increasing rates of water-cut and the pressure drawdown of horizontal well with different watercut stages was investigated. Finally, a practical method for determining the reasonable pressure drawdown of horizontal well after water breakthrough was obtained. This method is also given for horizontal well with edge water drive reservoir and will be applied to provide scientific reference with respect to controlling the overall increased rate of water-cut, determining the reasonable development plan and enhancing oil production by putting on drawdown to increasing liquid production.
Nowadays, horizontal well technology is widely applied to oilfield development, especially horizontal well can effectively delay the water cresting in developing bottom water driven reservoir. More and more theories and technologies have been developed for the development of horizontal well, Giger [1], Ozkan[2] et al and Papatzacos[3] et al developed the analytic model of critical rate and water breakthrough time for horizontal well respectively, Yang[4] et al and Recham[5] et al also presented the numerical model of critical rate and water breakthrough time for horizontal well using regression analysis of numerical simulation results. Dikken[6] first presented and modeled the pressure drop in horizontal well and its effect on the performance of horizontal well, then many authors (e.g. Penmatcha[7] et al and Ihara[8] et al) focused on the pressure drop in horizontal well and developed corresponding calculation models for horizontal well. Furui.[9], Hyun[10] and Penmatcha[11] et al studied the performance of horizontal well, and developed a coupled reservoir and wellbore model for horizontal well. Hyun[12] studied for integrated optimization on long horizontal well length, Fan[13] developed a model for optimal horizontal well length using a coupled model of reservoir and wellbore hydraulics, whereas Hu[14] presented that of model using NPV method. Jiang[15] et al discussed the water flooded performance and its effects on production performance of horizontal wells in TZ402CIII.
Horizontal well has advantage for high productivity. However, it will become the disadvantage once water breakthrough occurs. In fact, water breakthrough will occur absolutely in horizontal wells with bottom water drive, which would lead to many problems e.g. rapid increased rate of watercut and severe oil production decline once after water breakthrough, and nowadays it is lack of the feasible and effective matching technologies for stabilizing oil production and controlling water production.
