Practical Approach for Solid Production Prediction and Completion Strategy Decisions in Horizontal Wells – A Case study from Cretaceous Carbonate Reservoir – North Oman

Abstract

One of carbonate reservoir fields being produced by a large number of horizontal wells. The oil production wells are from long open hole section along the reservoir formation. The wells are completed by barefoot (open hole) completion with Electrical Submersible Pumps (ESP) located in wells build up section. The field has been experienced to significant ESP Failures, which has increased the operational expenditure (OPEX). Apart from scale build up, solid production from the open hole section is understood to be a crucial contributor to reduced pumps life. Several new wells are planned in the upcoming years, so the study aimed to provide input for the well completion strategy design and operational parameters (drawdown, flow rate), which could minimize the solid production and lower the intervention expenditure (OPEX). A Geomechanical assessment was carried out to assess the solid production from the open hole section. Geomechanical analysis based on analytical (elastic) solutions and modeling using Sand production tools was carried out. The results were calibrated with available field data and records of ESP failure in order to establish a link with geomechanical control on solid production. The analysis of rock mechanical properties show large variation of rock strength along the horizontal open hole section, which penetrated different rock types within the same formation. Drilling Rate of Penetration (ROP) data was reviewed which indicates variable rock strength along the horizontal well section based on variable ROP. Additionally, it was found that formation pore pressure was not constant along the wellbore and some portion of the reservoir was more depleted than the other. The model results show the most wells for a sustained period of time were subjected to drawdown of about 20-40% higher than the critical drawdown limit (for solid production). Field data showed that wells with significant depletion at the heel of the well-reported higher frequency of failures, but the wells with uniform formation pressure along the well, demonstrate relatively better performance in terms of ESP failures. Based on the study results, recommendations were provided on drawdown management strategy, which will potentially benefit from increasing ESP run life and reducing the field OPEX.