Holistic Approach for Effective Waterflood Management in Complex Reservoir in Middle East

Abstract

The presence of highly conductive thief zones causes poor volumetric sweep efficiency in waterflooding operations that might result in early water breakthrough and, hence, an increase in water production. Deep-reservoir profile modification is an effective method to force subsequently injected water to divert into low-permeability, oil-rich layers and to improve the sweep efficiency. This chemical water shut-off technology aids conformance control by plugging the high-permeability zones and diverting the fluid to the un-swept portion of the reservoir.

This work outlines a four-step holistic approach of identifying the conformance candidates and designing an optimal chemical to seal off highly conductive zones and divert the water to un-swept portion of the reservoir. Economic and technical success of conformance jobs is based on successful implementation of the improved workflow demonstrated in this work. A chemical treatment was customized to cross-link and permanently seal specific sections with any direct paths to nearby producers and allow a uniform distribution of injected water along the injection profile along the lateral. Production logging tool (PLT) data was used to identify the section with highest injectivity. The cross-linking time and pumping volume was designed once the zone was identified.

Coiled tubing application allows operators to reach deep zones, horizontal sections, and pump chemical treatment selectively in required zone/interval providing an efficient sealing of highly conductive zones. The engineered chemical treatment was injected form a protective ring in the formation with around 4 ft diameter. This will allow the injected water to migrate uniformly to other zones with lower injectivity rates and hence increase the sweep efficiency.

The holistic approach proved effective in enhancing the sweep efficiency. The flowrate of the well post operation was similar to pre-operation confirming good injectivity in the desired sections. A long-term monitoring program needs to be established to evaluate the water shut-off performance for future field development and planning. We expect an incremental hydrocarbon recovery by 5-10% oil OOIP (original oil in place).

The production data has proved the effectiveness of chemical treatment as an effective solution to enhance sweep efficiency of waterflood operations in terms of safety, economics, and operation. The novelty of this work like in its unique four-step holistic approach from identification to placement which allowed to inject the chemical treatment in required zone and avoid blocking other zone of interest. Coiled tubing application allowed to save considerable operational costs. Successful execution was achieved by integrated water management, strategic planning and technological innovation. This will play a crucial role in controlling lifecycle costs. Early planning is crucial to the success of water management. This technique does not require mechanically sealing off the perforations, making it more feasible for future well interventions.