[URTeC 2022] The Diminishing Returns of Lateral Length Across Different Basins (ID 3723784)

Abstract::

Objectives/Scope

Over the past decade, operators have significantly increased unconventional well performance through drilling longer laterals. While longer lateral length is known to benefit production, the exact efficiency of the additional length is a subject of much debate, in part due to the difficulties in separating the impact of longer laterals from upsized completions, interwell spacing, and geology. In this study, we use machine learning to disentangle the complex, nonlinear relationships to generate estimates of lateral length production efficiency across the major unconventional plays in the US.

Methods/Procedures/Process

We created a dataset for horizontal wells in six different basins, the Delaware, Denver-Julesburg, Eagle Ford-Gas Window, Eagle Ford-Oil Window, Midland, and Williston basins. For all regions, we built a basin-specific ensemble of decision tree models that utilized lateral length, completions, geology, and spacing as input features to predict three-year cumulative oil/condensate production. These models are then used to forecast a multitude of hypothetical wells placed throughout each basin.

For each basin, a lateral length efficiency curve is created using the relative performance degradation for increasing well lengths when comparing against the results from wells with 5,000 ft. This study reveals that increasing well lengths does not result in proportionate production gains. In fact, in some basins a 2-mile-long lateral only produces 85% of the normalized production of 1-mile-long laterals. We also find that the size of the completions job can influence the shape of the lateral length efficiency curve.

Applications/Significance/Novelty

Oftentimes operators are planning for future wells with very long laterals without adjusting expectations on production per foot. However, for every basin in this study, we demonstrate there are varying magnitudes of diminishing return on production per lateral foot. Asset valuations need to take each PUD’s length into account and adjust projected reserves accordingly. Similarly, for certain basins, planners will need to carefully weigh the costs and risks of drilling long laterals vs the outcome of drilling two separate wells.