Operators in the Permian Basin continue to advance their knowledge on unconventional horizontal wellbore constructions. Motivations to drill and complete the longest possible laterals could come from either maintaining lease agreements held by production or reducing costs. Therefore, analyzing production effects over time due to trajectories is necessary to advance our understanding of production optimization. This paper aims to determine optimal lateral lengths and trajectories in the Permian Basin by studying the impact of the lateral length and trajectory on well performance.

This study covers additional applications on the impact of lateral lengths and trajectories on University Lands Delaware Basin wells. We couple reservoir simulation models with transient multiphase wellbore models. The reservoir simulation model is calibrated with production histories. The calibrated model is then used to forecast the long-term well productivity. This paper details the following multiphase flow simulation cases:

  1. horizontal wellbores with vertical deviations, and

  2. horizontal wellbores with vertical deviations and tortuosity, combining with different lateral lengths, and reservoir and production conditions.

These new case studies confirm that uniform, toe up wells could yield higher productivity and production potential. However, the study also reveals that long lateral lengths do not completely ensure proportionately more production, the toe-up configuration could yield higher liquid recoveries, but not always oil recoveries. Additionally, a high degree of wellbore tortuosity could hinder production potential. Fluid properties, such as water cut and GLR, could influence recoveries per lateral length when drilling longer laterals. For instance, wells producing fluid with high gas-to-liquid ratios could produce less than twice the EUR at double the average lateral length compared to the EUR at an average lateral length. However, wells producing fluid with low gas-to-liquid ratios could produce roughly twice the EUR at double the lateral length. The paper also discusses how liquid holdup also contributes to these results.

Wellbore lateral lengths and uniformity are important for production optimization to minimize liquid holdup and maximize productivity throughout the wells' production lives. However, wellbore construction designed for holding leases and completed under time constraints could negatively impact production and limit operators' potential for their acreage. To determine an optimal lateral wellbore length, it is necessary to study wellbore multiphase flow behavior, isolate the wellbore hydraulics to evaluate its significance, and resulting production for unconventional horizontal wells.

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