Well Test Analysis For An Inclined Multiwell System

The technique of the vertical or horizontal well test analysis has been widely applied in petroleum industry, and it plays an important role in reasonably and efficiently developing different kinds of oil fields. However, along with the complexity of the ground conditions in main oilfields onshore and the expansion of exploratory development offshore, inclined and directional wells are increasing tremendously. Currently, there is not inclined well test analysis software in petroleum industry. The inclined well test data are usually analyzed by the vertical well test analysis software. Moreover, many inclined wells are usually clustered, whose data must be processed by multi-well test analysis software. But no multi-well test analysis software can be applied in the market. Based on the situation above and literature research, this paper presents a complete set of inclined multi-well test analysis methods, which were successfully verified by computational examples in the field. The key work is summarized as follows:1. An efficient algorithm is presented to compute transient pressure response for an inclined well in nonuniform infinite slab reservoirs with dual porosity behavior. This algorithm performs over an order of magnitude faster than the traditional methods. The efficiency and accuracy were verified by a number of computational examples.2. This paper presents a powerful algorithm to calculate the transient pressure responses of an inclined multi-well system, in which the inclination angle, changeable production rate, pattern arrangement, and number of wells can all be arbitrary. The algorithm can be applied to interpret the well test data obtained from neighbor inclined wells whose production rates are changeable. The algorithm was verified by computational examples.3. A theoretical formula and an efficient algorithm are presented to solve the equivalent pressure point of an inclined multi-well system or horizontal multilateral well consisting of inclined branches. The algorithm was verified by computational examples.4. This paper presents a method of processing inclined well data of partially penetrating formation by means of the vertical well test analysis software and pseudo skin coefficient. The conditionality of how to apply the method has been demonstrated by a number of computational examples. The support vectory machine was applied to derive pseudo skin correlation that is applicable for inclined wells with all inclined angles and partially penetrating formation.5. The typically automated curve matching method with the first and second derivatives has been proved to be Newton-Raphson iterative algorithm. Based on fractal theory the reasons of multi-solution or non-solution generated by the derivative methods have been analyzed and explained. For multi-solution reality an efficient algorithm to calculate multiple global optimums and a non-linear programming algorithm are presented, and the algorithms were verified by computational examples. The inclined multi-well test analysis was verified by a set of field data as well.