Well Placement Assessment Using Sequence Stratigraphic Zonation in a Complex Carbonate Reservoir

Abstract

The paper is continuation of our previous work published in the SPE-192896. This work illustrates horizontal well placement sensitivity analysis that was conducted on a complex Valanginian (Cretaceous) unsaturated oil carbonate reservoir with strong water drive. Existing producer wells are 80% horizontal and the remaining 20% are vertical to deviated producers. The production history is the approximately 20 years and currently a peripheral water injection is implemented, all injector wells are horizontals. The well placement is very challenging due to the presence of some thin high permeability streaks intervals with permeability value of up to 1 Darcy. Early water breakthrough encountered in the existing oil producers is a serious problem which results in lower recovery factor and costly lifting treatment. In addition, premature breakthrough would leave behind the potential oil accumulation. Therefore defining the optimum placement location of the producers is a crucial decision to be decided during well plan and field development. In this paper we applied novel approach for stochastically modeling complex carbonate reservoir lithofacies and properties distribution using a pre-defined High Resolution Sequence Stratigraphy (HRSS) model subzonation. The key static geological elements that must be well defined are HRSS framework, lithofacies architecture, and field wide rock properties. In this study, we apply integrated geosciences, geostatistical, and flow simulations to assess options for well placement. This new holistic approach has recently been successfully implemented in the studied field. The resulted geostatistical model was able to explain pressure depletion and production rate as shown in historical production data of the field. The resulting dynamic model will hence provide reliable production forecast and reservoirs development plan which will eventually allow accomplishing the mandate recovery target. Flow simulation was used to analyze the performance of the well considering horizontal the well azimuth, well inclination, wells length, wells position relative to the sequence stratigraphic zonation, and well position relative to the water contact. In addition, multi-scenarios of well placement were created to see the impact on the oil rate, plateau, and water breakthrough time. Some producers in the studied reservoirs have been drilled using the multidiscipline study recommendation. Actual property and rate derived from the newly drilled wells displayed a very reasonable match to the expected property from the model.