Theoretical derivation and application research of stepped horizontal well patterns with coupling reservoir/wellbore flow in multilayer reservoir

It is quite difficult to apply the regular well patterns into the development of oilfields due to a series of factors like the geology complexity, the limitation of development cost and the operability in real reservoir. Therefore, a new kind of well pattern is proposed to deal with the above problem. This method focuses on developing multilayer reservoir by the stepped horizontal well, which is deployed with two vertical injectors at both sides, respectively. According to the newly established well pattern, the corresponding productivity formula for the stepped horizontal is deduced. In this process, the stepped horizontal well is divided into several sections by each layer in the first. Secondly, the productivity equation of one section among them is derived on the basis of conformal transformation and potential flow theory, the other section is dealt with in the same way. Thirdly, the simultaneous equations of productivity for each section are solved on the basis of nodal analysis. Besides, the pressure drop loss of wellbore flow in the horizontal section is also taken into consideration. Finally, the total productivity is worked out. In order to prove the applicability of the established productivity formula for the proposed well pattern, the data of well Z12-33 in Zhaozhou oilfield are adopted to calculate the total productivity, the results indicate that the error between calculated value and real production is small, which proves the reliability of this formula. Therefore, this formula can be applied into the real reservoirs to aid the oilfields development.