Improving Fluid Loss Control During Well Intervention; A Case Study on the Use of Innovative Salt System

Abstract

Kuwait heavy oil development target reservoir is a shallow, sub-hydrostatic and unconsolidated sandstone with relatively high porosity and permeability. Due to nature of this reservoir, well intervention operations in North Kuwait Heavy Oil Asset exhibit a higher risk of significant fluid loss that causes wellbore impairment, incremental operational costs, excess brine volume usage, and more importantly a significant impact on production deferment. The latter is due to formation damage and the time required to produce the completion fluid that is lost to the reservoir during any well intervention. The objective of using a cost-effective and less non-damaging fluid is achieved by the application of a novel customized salt system that was successfully trialed in the field. A systematic research was employed to find a suitable product/system that could be used in sub- hydrostatic conditions, able to effectively control fluid loss while retaining as near the original permeability. This new system and subsequent formulation adhered to the following criteria: Readily available Cost effective Easy to formulate and pump Easy to circulate out No long-term formation damage thus retaining original formation permeability The success of this fluid loss control material is indicated by a constant fluid level at surface after application thereby confirming its effectiveness in meeting the desired objectives. This salt system application was successfully field tested, and the results were satisfactory. During well intervention operations, the system effectively arrested fluid loss as confirmed by the fluid level measured at surface. Post operation, the well was brought back immediately to its original rate thereby confirming little to no permanent reduction to reservoir permeability. Historically, during well interventions in Kuwait Heavy Oil field, dynamic loss rates measured were in the 100 to 120 bbl per hour range. Post application of this salt system showed fluid loss rates ranging from 3 to 4 bbl per hour. To date no post acid stimulations were required to restore well production to original levels. This system was readily adapted for thermal application and compatibility with existing fluids, good bridging characteristics, as well as flow-back enhancement. This approach eliminated additional AFE costs by minimizing dynamic losses.