The variability of reservoir properties across the lateral section of horizontal shale wells remains a prevalent phenomenon that has been observed in the development of numerous unconventional plays. However, the majority of wells in these plays are completed geometrically without account for the heterogeneity present across the wellbore thereby resulting in non-uniform production profiles along the length of the wellbore. This assertion is further validated by production logs from over 250+ horizontal shale wells which show that only about 60% of perforation clusters contribute to production in these wells, meaning 40% of the wellbore are not effectively stimulated. In recent years, operators have improved upon the geometric completion technique using an engineered approach which has resulted in better completion efficiency and production performance.
This paper presents a case study of a horizontal well drilled in the Marcellus shale and equipped with a permanent fiber optic cable to investigate the effectiveness of the engineered completion approach compared to the standard geometric method. For this evaluation, the lateral length of the horizontal study well was divided into different sections. One section of the lateral employed geometric perforation placement while the perforations on another section were designed using an engineered approach. To address the challenges of perforation placement introduced by the fiber-optic cable, an enhanced perforation design methodology was implemented which leveraged the available geomechanical properties along with the wellbore and fiber-optic configurations, perforation gun specifications, and stimulation treatment design parameters to predict perforation breakdown pressures along the wellbore. Using the predicted breakdown pressures, the limited entry technique was then applied to engineer the perforation strategy for each of the stages to improve the likelihood of initiation from all of the perforation clusters. The distributed temperature and acoustic measurements from the fiber optic cable were then analyzed during the fracturing treatment to provide insight into which of the perforation clusters were initiating hydraulic fractures and being effectively stimulated.
Observations from the fiber optic data consistently showed that all perforation clusters were immediately initiated for the engineered stages with uniform acoustic energy distributions occurring across all clusters which further indicated uniform stimulation across all of perforation clusters. For the geometric stages, only about 40% to 60% of the perforation clusters became activated with intermittent acoustic energy distributions being observed across all clusters throughout the treatment stages.
The case study discussed in the paper presents and validates a novel approach for improving the wellbore stimulation coverage in an unconventional development. Through the characterization and incorporation of reservoir heterogeneity into the engineered completion design workflow, completion efficiency can be improved leading to enhanced well performance and project economics.