Suitability of Horizontal, Inclined, and Vertical Wells on an Indian Offshore Platform Using Pressure Transient Analysis

Abstract

Abstract The Indian offshore field under study has "LA" reservoir as one of the main producer. While the testing was carried out, nearly 20 wells were completed out of which 17 were on production, producing about 18,000 BOPD. "LA" reservoir is relatively clean and well developed in the crestal part of the reservoir. The average thickness of "LA" reservoir in the crestal part is 35-40m and increases upto 70m towards the flank. The Gas Oil Contact and Oil Water Contact are at 940m and 740m from MSL respectively. The IOIP and IGIP are of the order of 100.6 MMt and 2297 MMm3. In order to ascertain productivity of horizontal well, maximise oil recovery, prevent possible gas and water coning besides mastering of the technology, it was proposed to drill two horizontal wells. This paper studies the Pressure Transient data of the Horizontal, Inclined and Vertical well of the same field. The interpretation of the horizontal well testing data was more complex due to development of shorter flow regimes. The data, however, is carefully analysed using the available software to determine several parameters including the average permeability and "k.h" product. The diagnostic derivative plots are used to determine the different flow regimes. Using the results, the permeability anisotropy and specific productivity was calculated for each well system. Replacement Ratio of horizontal to vertical/inclined well was determined using Newton's mid-pt numerical method and the cost analysis was done. Replacement Ratio and Cost ratio was combined for comparison of the three well systems. Replacement Ratio was determined to be 2.25 which means 2.25 vertical wells may replace 1 horizontal well with same rate of production while Cost ratio for horizontal to vertical well was 2.40. On combining the two, it implied that horizontal well system was marginally more suitable in addition to other benefits for the given field with given conditions which in other words signifies that the horizontal well system's efficiency wasn't upto the desired level and needs severe improvement.