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Impact of Lateral Placement on Well Performance in the Bakken Play

Abstract

High costs of field development in unconventional plays, like the Bakken, place a premium on understanding and maximizing well performance. While many things are beyond our control, lateral placement and completion design can be determined and have a significant impact on well performance. This study documents the impact of lateral placement within the Middle Bakken reservoir on well performance. Internally, the Middle Bakken reservoir is composed of two sequences, an undifferentiated Lower Middle Bakken sequence and an Upper Middle Bakken sequence that is further partitioned into three systems tracts. Each of these four sequence stratigraphic units contains a distinctive assemblage of facies characterized by expressly different hydrocarbon saturations and reservoir properties as observed in conventional cores. Fifty-eight Middle Bakken laterals were evaluated within this stratigraphic framework to determine the impact of lateral placement upon well performance. Wells were selected to be of similar vintages, completions types, and geographic areas as to limit other factors affecting performance. Analysis of well reports, mudlogs, and post-drill geosteering was conducted to place each lateral into the stratigraphic framework. Two geologic based factors emerged as having the greatest impact on well performance: 1) placement of the lateral in relation to higher quality reservoir with higher oil saturations, and 2) the geomechanical properties immediately surrounding the wellbore. Principal Component Analysis and other statistical methods were used to place the wells into one of four groups. Group 1 was considered to be optimally targeted by reservoir, Groups 2 and 3 were considered to have been sub-optimally targeted with respect to reservoir, and Group 4 was considered to have been sub-optimally targeted with respect to known geomechanical boundaries. With the first 90 days of production as a benchmark, the optimally placed Group 1 wells outperformed Group 2 and 3 wells by an average of 5-24%. When Group 1 wells are compared to Group 4, introducing geomechanical problems, the ideally targeted group outperforms the sub-optimally placed laterals by an average of 32-44%. With steep declines, this initial gap in production can have a significant impact on the EUR of these unconventional type wells. It also shows the importance of geologic understanding when designing and optimizing efficient, cost-effective completions strategies for unconventional plays.