Getting the Most Out of Coalbed Methane Pilot Testing - Learnings from More than 15 Years in Queensland
Authors: Jones Alistair , Yang Shuyan 
Published: October 2024

Extended production testing of pilot wells is traditionally a key step for appraisal of coalbed methane (CBM), also known as coal seam gas (CSG), fields. Several of Australia Pacific LNG (APLNG) CBM fields in Queensland Australia have transitioned from exploration to development and some have more than a decade's worth of production data. This study reviewed over a hundred pilot wells across 23 pilot programs that took place between mid-2000s and late 2010s, with a focus on pilot programs that led to subsequent development in their respective areas. The objective of this study is to assess the pilot programs to identify key lessons for future pilot developments.

This examination encompassed the impact of the design of pilot programs, evaluation of pilot performance, insights on what worked and what could have been done better, and assessment on whether the value of the pilot was achieved.

For pilot programs that led to the decision to develop their respective fields, comparisons between the pilot performance and nearby development well performances were made. It was found for pilots in the Surat Basin, the pilot results often did not demonstrate the field's production potential. In some cases, this discrepancy can be attributed to the limited coal de-watering achieved by the pilots compared to the de-watering achieved by the additional wells and production time of a full field development. In other cases, the difference was due to the heterogeneity of the Surat Basin coal seams.

Five-spot pilots were compared to single-well pilots and it was found that the theoretical benefit of five-spot pilots was not necessarily achieved due to significant coal heterogeneity. The support provided by the four corner wells to enable the centre wells to be the best performing wells was limited. In addition, single-well pilots were able to reduce cumulative water-gas ratio to a similar level of those in five-spot pilots, indicating a similar level of de-watering effectiveness in the Surat Basin.

Pilot results were often delayed and sometimes put in jeopardy by low well uptime. The top two causes for low well uptime were related to downhole issues and surface water handling limitations. Implementing a comprehensive response strategy for downhole failures, allocating sufficient resources for timely interventions, and aligning workover priorities across all stakeholders were the crucial steps identified to reduce the time taken to bring a pilot back online.

Lastly, a review of pilot program investment decision documentation found that objectives were not always clearly defined. Pilot testing should not be undertaken just because it is a standard appraisal activity for CBM. It is important to have the objectives clearly defined upfront, including operational and commercial success criteria for each pilot program articulated. This is to ensure that the pilots are designed and operated to meet the operational and commercial success criteria, and therefore provide positive value of information. In addition, a decision to complete the pilot testing can be made with reference to the criteria defined upfront.