Shale well factory model reviewed: Eagle Ford case study

Abstract

This case study highlights that shale wells drilled with close well spacing in the same landing zone in the same reservoir rock, using the same fracture treatment plan and parameters, commonly show large variances in well productivity. Searching for the root cause(s) of this variance in performance, we conclude that the factory model -- which assumes wells can be engineered in reproducible and identical ways using the same treatment plans -- is not yet feasible in practice. A thorough analysis of production data from wells completed in the Eagle Ford Formation shows variations in cumulative oil production cannot be attributed to lateral length, the number of hydraulic fracture stages or fluid/proppant load due to the almost constant values used in keeping with the “Factory Model” drilling method. Based on the dataset available, other parameters for the discrepancies in production volumes are proposed. Some parameters such as (1) reservoir quality and (2) well production control have been determined to have very low impact on production rates variability, while others such as (3) production timing, and (4) water cut may have a more moderate effect. The last defined parameters of (5) fracture quality/performance, and (6) well spacing are determined to have the largest impact on the cumulative production and were concluded to have the highest probability of being the main drivers behind the variations in well productivity. Use of production data with the Complex Analysis Method (CAM) to produce spatial drainage plots also provides insight into recovery factors from these wells. CAM results reveal relatively small, drained rock volumes (DRV) around the modeled hydraulic fractures, which is typical for unconventional shale wells.