Abstract
In the process of oil field development, the law of water cut is usually described by exponent model, but during the early water breakthrough stage and ultra-high water cut stage, relative permeability ratio of oil to water (<i>K<sub>ro</sub>/K<sub>rw</sub></i>) and water saturation (<i>S<sub>w</sub></i>) is no longer linear relations in semilog coordinate, so it has an important influence on water cut increasing rate, theoretical production index, oil displacement efficiency, relationship between recovery and water cut etc. Based on relation curve character of relative permeability ratio of oil to water (<i>K<sub>ro</sub>/K<sub>rw</sub></i>) and water saturation (<i>S<sub>w</sub></i>), this paper proposes a new function model in order to reduce prediction error, such as production index and water cut increasing rate. According to nonlinear properties of the model, Newton algorithm is supposed to be used for optimization solution. Finally, take relative permeability data of P Oilfield as an example to testify, and results show that fitting precision of the model is quite high and it possess nicer applicability. On this basis, the relationship between water cut and recovery, relationship between water cut increasing rate and recovery are derived. By comparing water cut and water cut increasing rate with recovery degree, it can be used to guide the development as the foundation of geology and reservoir of P Oilfield.
Highlights
Evaluate water production law of oil production well is a key point in oilfield development
Equation (2) shows that viscosity ratio of oil to water can be considered as a constant value for a specific reservoir, so relative permeability ratio determination is important to water cut
Take relative permeability data of P oilfield as an example, which is illustrated in Table 1 and Figure 2, this paper studied relation between water saturation and relative permeability ratio of the area
Summary
Evaluate water production law of oil production well is a key point in oilfield development. The precision of water cut forecast will affect reservoir engineer’s right decision. Water cut percentage fw is a significant evaluation parameter to describe water production law, without considering the influence of gravity and capillary pressure, according to the flow equation, it is calculated as follows: Q f w wQ Q. The water cut percentage fw of ground which is converted by volume coefficient is calculated as follows: f. Equation (2) shows that viscosity ratio of oil to water can be considered as a constant value for a specific reservoir, so relative permeability ratio determination is important to water cut. How to define functional relation between Kro/Krw and Sw will decide forecast precision of water cut in oilfield development
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