Abstract
Acid stimulation is an excellent method to increase hydrocarbon production and long-term formation drainage from carbonate formations. However, the stimulation effectiveness largely depends on pertinent placement method. Besides the necessity for optimized treatment design and fluid recipe, homogenous acid distribution is one of the most critical aspects for treatment success. For this purpose, a novel completion method has been deployed that allows for effective acid stimulation by maximizing formation contact in the openhole horizontal wellbore.
An improved Multistage Stimulation System (MSS) that has been developed to distribute acid homogenously across the lateral is utilized, where multiple sleeves are deployed in clusters as part of a single stage, and opened with a single size ball without being limited to pump rate. It was considered imperative to have positive indications of the balls landing on the seats and the sleeves being shifted open within the zone of interest. The previous MSS system was based on severing part of the nozzles for fluid access which needed to be upgraded for better operational efficiency and production enhancement.
The new completion technology is suitable for carbonate formations which are tight, heterogeneous and require stimulation to improve gas production and recovery. Wells drilled in the maximum horizontal stress direction to mitigate hole stability risks and geosteered to maximize the formation contact makes it difficult to stimulate effectively. Therefore, an improved MSS system is required to homogenously distribute the acid across the lateral during the stimulation. This novel MSS completion design was undertaken standardized, well established trial test procedure and was applied in a candidate well and included three stages where two of the stages utilized four sliding sleeves while the remaining stage was integrated with five sliding sleeves. Each stage was isolated by hydro-mechanical packers in the 5.875 in openhole.
Each stage was then monitored using a new surface mounted real-time downhole monitoring system, an electronic device that enables live verification of completion operation events while being independent of pressure. The data gathered from different sources indicated that the sleeves functioned as per design. The production results exceeded the expectations.
This paper describes a novel approach that enhances acid stimulation effectiveness and fulfills stimulation objectives using advanced openhole MSS completion technology. Evolution of the technology and comparison with its predecessor is discussed. It also demonstrates the use of a new surface monitoring system that supplies real time data during sleeve activations enabling clear and accurate detection of downhole events.
