Use of ICD Wellbore Models to Improve History Match in ICD Completions

Abstract

Obikpo field was discovered in the late 1960s, and since then over 40 wells have been drilled. By the end of the year 2018, more than 68 MMstb oil would have been produced from the field. Water cut has risen to over 65% and this affects performances of oil wells. The field is geologically complex, heterogeneous and divided by large faults; leading to local permeability enhancements that most times serves as barriers to uniform fluid displacement. Average gross thickness of the reservoir is about 80 ft. Recovery is mainly by the strong bottom water influx, expansion and secondary support from water injection. Obikpo fluid typically is heavy in nature resulting in poor mobility ratio which keeps the water table irregularly distributed across the sands. To improve on the recovery across Obikpo field, Inflow Control Device (ICD) technology is being utilized in all Obikpo wells to mitigate heel to toe coning effects and channeling / fingering of unwanted water into completions. Inflow Control devices are passive flow control devices installed in the completion sand face to alter fluid production near the wellbore by either creating a uniform influx into the wellbore or delaying unwanted fluid breakthrough. Obikpo 33, like other wells in this reservoir, was completed with ICDs and this paper discusses the history matching of Obikpo 33 well. The objective of every history match is to accurately determine the distribution of the oil remaining in the reservoir to help predict the performance of existing and future wells. The typical reservoir model is built on a large scale and this does not typically incorporate near wellbore fine details such as the ICDs. Running a history match (HM) of the reservoir without incorporating these ICDs into the field model may lead to certain parameters being wrongly modified to match late water breakthrough and lower water production because the ICDs create a pseudo distributed productivity effect in the horizontal which alters the natural fluid flow pattern within the near wellbore region. Matching water breakthrough in this well using conventional HM techniques failed due to ICD design and segmentation not incorporated into the model. To account for this effect the ICD wellbore model is coupled with the reservoir model using a multi-segmented well modelling approach, this enabled the calculation of the additional pressure drops in each well segment arising from the varying nozzle sizes along the lateral. This achieved regulation of water influx from the reservoir boundaries and channels by automatic distribution of flux along the lateral. This approach gave excellent results in history matching of Obikpo33 and thus presented a reliable prediction tool for forecasting reservoir performance. The simulated results also confirmed that the delayed water breakthrough and lower water production observed during the production life of the well is due to the ICD nozzles installed in the completion. The presented workflow and method are applicable especially for heterogenous reservoirs under strong water drive.