Screening Study for an Optimal Horizontal Section Length of a Maximized Reservoir Contact Well

Abstract

Abstract Reservoir development using Maximum Reservoir Contact (MRC) wells has taken significant leaps and bounds in the oil and gas industry in the last fifteen years with horizontal well length of more than 2500 meters. MRCs, a breakthrough in drilling technology, has enabled us to drill long horizontal producing or injecting sections, especially in low permeability or tight oil bearing layers. In such reservoirs, with the increased reservoir contact surface area, the wells are able to produce and inject at higher rates with lesser drawdowns. This increased productivity index helps to delay the gas and water breakthrough, reduce the conning and improve the GOR/Water-cut response. Hence, improving the sweep efficiency and the ultimate recoveries. On the other hand, MRC wells could potentially help to address the subsurface and surface congestion challenges especially in brown fields by reducing the overall development well count by 2 to 3 times. The production gain from long horizontal section is limited by the pressure drop within the well bore from toe to heel. Therefore, there is a technical limit to the production gain that can be achieved by increasing the horizontal section length. Drilling beyond this limit will incur cost without any prominent production gains. Hence, there would be a techno-economic limit to the optimal MRC well length. This paper present the screening study conducted to determine the optimal well length for an MRC well from a techno-economic point of view. A mechanistic fine gridded sector simulation model is used for this study. The MRC wells are segmented and considers the well bore hydraulic calculations for all the pressure loss elements. Different MRC well length scenarios are considered to compare the sweep efficiency and ultimate recoveries. The cost to benefit screening analysis is conducted for various MRC lengths, in relation with their associated costs and dynamic performance. The techno-economic analysis indicates that the MRC well length of around 10K ft is the optimal. Beyond this length, there is a marginal increase in incremental NPV and the relative difference in reduction of UTC gets minimal. The paper highlights the importance of a value assurance study conducted for the MRC well lengths that can potentially be considered for optimal field development/re-development. Each reservoir with its specific rock and fluid characteristics would worth this type of screening study with the help of numerical simulation tools. The choice of MRC well length would eventually have a great impact on the field development economics.