Effect of Horizontal Well Trajectory on Two-Phase Gas-Liquid Flow Behavior

Rosmer Brito-Smith, Research Assistant, Ph.D. Candidate

Shale reservoirs ordinarily have insufficient permeability to allow significant amount of fluid flow to the wellbore.  In order to produce from shale reservoirs, horizontal or deviated wells are drilled and hydraulic fracturing is performed to improve the formation conductivity.  Typically, geologists and reservoir engineers design well trajectory based on gas rate while drilling.  They “surf” up and down to get a good permeability steak (Jackson et al. 2011).  Consequently, wells are not horizontal, and rather in different trajectories, such as toe-up, toe-down, undulations or more complex configurations.

Well trajectory can significantly affect the gas-liquid flow behavior, increasing or decreasing the probability of erratic production conditions such as liquid loading, water accumulation in the lateral section, start-up, terrain, or severe slugging along the well.  These erratic production conditions can generate operational problems such as: reduction in well production, intermittent flow, no-flow, faster mechanical fatigue along the completion or surface equipment, shorter run-life of the artificial lift system, reduction of stimulated reservoir volume and fracture conductivity due to water imbibition, scale precipitation or shale swelling.  This justifies the need to evaluate the effect of well trajectory on two-phase flow.  Additionally, the acquired knowledge could help to optimize the well trajectory and minimize drilling operation cost and time.

The main objective of this study is to perform an experimental and modeling study of air-water two-phase flow in near-horizontal gas or condensate wells. The effects of well trajectory will be investigated on two-phase flow behavior. This study is divided into the following phases:

  1. Experimental Program: A 2-in. ID experimental facility was constructed and is used to evaluate the flow behavior for different well configurations namely, toe-up, toe-down, and one-undulation cases.  Additionally, different gas and liquid flow rates are considered to mimic the reservoir pressure decline, and varying liquid inflow from the reservoir. 
  2. Unified Mechanistic Model development for all inclination angles: The target is to predict the flow pattern, pressure drop, liquid holdup and erratic conditions such as liquid loading and slugging. 
  3. Validate model performance using experimental and field data. 
  4. Compare model performance against existing liquid loading onset models and OLGA simulations.

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