Suboptimal completion design leads to understimulation of perforations

Historically, operators in the Marcellus Shale have relied on geometric staging and perforating techniques to complete their horizontal wells. Generally, when using these techniques, perforation clusters are placed at equidistant points along the lateral. However, extensive microseismic monitoring and production logging studies conducted on geometric wellbores have indicated that large sections of these laterals are being left unstimulated, thereby leaving behind untapped gas reserves.

In recent years, an engineered completion approach has been adopted by shale gas operators in the northeast region of the US. Using the Mangrove stimulation design, this technique bases the staging and perforating design on lateral measurements that are acquired either by wireline or logging-while-drilling (LWD) services. Placing perforations in reservoir intervals with similar geomechanical and reservoir properties allows for more-uniformed distribution of the stimulation treatment into each of the clusters, thereby improving the likelihood of more clusters contributing to production.

To evaluate the success of the engineered completion approach to staging and perforation placement, a production study was performed in which a group of engineered wells was compared with nearby conventional geometric wells.

Integrated additional data for improved completion design

For the five wells engineered using Mangrove stimulation design, the stress along the lateral section of the well was computed using either the Sonic Scanner platform or the sonicVISION service’s LWD platform. The data collected was used to identify areas of probable high or low stresses, which could then be avoided or targeted, respectively. Perforation clusters were then located to reduce the stress contrast within a given stage.

Improved production in engineered wells

While the initial results showed immediate improvement in production, the study continued to monitor the production. After 18 months, the five engineered wells on average produced in the top 30 percentile, with an additional 31 MMcf per 1,000 ft [305 m] of lateral length on average compared with the nonengineered wells. For a typical Marcellus well of 6,000 ft [1,829 m], this increase represented an incremental increase in revenue of USD 558,000, assuming USD 3 per Mcf for gas.