Abstract
A mature field similar to the Greater Burgan field in Kuwait brings many challenges. The Kuwait Oil Company (KOC) has determined that the production from the Burgan oilfield of South & East Kuwait required to be maintained as per the production plan. Often, the unavailability of suitable surface locations posed several challenges, and drilling was one of them. A new approach helped to address these issues which otherwise delayed production. The Lower Cretaceous Burgan sands are divided into five main reservoirs; two reservoirs consist of stacked, massive fluvial channels, while the remaining three mostly consist of deltaic distributary channels and bays in a tidal delta setting, grading to shallow marine. These three reservoirs are also discontinuous, both laterally and vertically.
Every year in the Greater Burgan field, a large number of wells are drilled targeting the Cretaceous reservoirs. The Greater Burgan field has been producing for more than 60 years. Due to the unavailability of suitable surface locations, highly deviated wells are drilled, and to reach them at target reservoir, the well profile sometimes passes through faults which create partial or total losses while drilling, which results in badhole condition. In some of the wells, owing to poor hole conditions, recording openhole logs are not possible. Normally in such cases where openhole logging is not possible, PNC logs are carried out. However, recording of PNC logs is only possible after 2-3 months when the effects of mud invasion and mud filtrate are reduced to a minimum. However, this delays production.
Openhole logging had to be abandoned in one of the recently drilled wells, due to poor hole conditions. Resistivity Behind Casing tool (RBC) was proposed to be run in this well as a replacement for the PNC log. The RBC provides the measurement of reservoir bed resistivity in order to determine the oil saturation for estimating reserves. The RBC uses stationary measurements where the tool’s probes apply current to the steel casing. The current that is leaked into the formation is then measured and processed to determine the formation resistivity. The tool has a depth of investigation of 7 to 34 ft depending on the bed thickness and is therefore not influenced by the effects of mud invasion.
Based on the casedhole resistivity, potential intervals were identified, perforated and were put on early production. Casedhole resistivity paved a way for replenishment of missing data on openhole electrical logging. This has enabled early production from a well with badhole issues.
