Introduction Of A New Well Design To The Narrabri Coal Seam Gas Project
- Mike Cunnington (Eastern Star Gas Pty Ltd) | Linda K. Hedger (EarthReach Coal Pty Ltd)
- Document ID
- Society of Petroleum Engineers
- SPE Asia Pacific Oil and Gas Conference and Exhibition, 18-20 October, Brisbane, Queensland, Australia
- Publication Date
- Document Type
- Conference Paper
- 2010. Society of Petroleum Engineers
- 1.10 Drilling Equipment, 1.4.1 BHA Design, 3.1.7 Progressing Cavity Pumps, 1.14 Casing and Cementing, 1.12.1 Measurement While Drilling, 1.11 Drilling Fluids and Materials, 1.10.1 Drill string components and drilling tools (tubulars, jars, subs, stabilisers, reamers, etc), 1.6 Drilling Operations, 4.3.4 Scale, 1.7 Pressure Management, 5.7 Reserves Evaluation, 4.6.2 Liquified Natural Gas (LNG), 1.1.3 Trajectory design, 1.12.2 Logging While Drilling, 1.5 Drill Bits, 1.4 Drillstring Design, 1.6.6 Directional Drilling, 1.1 Well Planning, 1.7.5 Well Control, 5.8.3 Coal Seam Gas, 5.6.1 Open hole/cased hole log analysis, 5.5 Reservoir Simulation, 5.1.2 Faults and Fracture Characterisation, 1.8 Formation Damage, 4.2 Pipelines, Flowlines and Risers, 3.1 Artificial Lift Systems, 4.1.2 Separation and Treating, 6.1.5 Human Resources, Competence and Training, 1.6.1 Drilling Operation Management, 1.6.7 Geosteering / Reservoir Navigation, 1.5.5 Ranging Tools and Proximity Calculation, 1.14.1 Casing Design, 4.1.5 Processing Equipment, 3 Production and Well Operations
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Reservoir studies indicated that horizontal wells drilled in seam and intersecting vertical production wells were the optimal design to produce coal seam gas from the Narrabri CSG Project. An aggressive campaign of production pilots was drilled in 2009 and early 2010 to prove the potential of three coal seams in the Project area. The pilot wells included two dual lateral horizontal wells, with each horizontal well intersecting three vertical wells; a tri-lateral horizontal well which intersected four vertical wells; two long and three short single lateral horizontal wells intersecting one vertical well each; and three short, single lateral horizontal wells drilled from a single drilling pad to intersect three vertical wells. The importance to the company of the results required a high degree of certainty in well construction success.
There was very little time for rig start up issues to be addressed before the first horizontal well was drilled and early development of a competent wellsite team was essential. With little precedent and many unknowns, a low risk, fully engineered approach to the well design and drilling operations was adopted.
Connection of the vertical and horizontal wellbores is critical, and intersection techniques have been developed and refined. The Rotating Magnet Ranging System was introduced to Australia for this project, and adoption of this technology has subtle implications for directional drilling equipment and techniques. The wellbore hydraulics design and management while drilling program differed in several respects to conventional horizontal drilling, and performed very well.
The selection of the rig package, down-hole equipment and personnel underpinned the success of the 2009 - 2010 drilling campaign, and is described. The technical standards developed by the operation will interest other coal seam gas operators who face the challenge of economic extraction of coal seam gas, particularly from anisotropically fractured or deeper, lower permeability coals.
The Narrabri Coal Seam Gas Project is located in PEL 238, near the township of Narrabri in north western NSW, Australia. Until 2005 the permit was explored mainly for conventional petroleum reservoirs by a series of operators. Gas was discovered within thin, sandstone reservoirs in small, anticlinal structures and produced to supply a small power station feeding into the local electricity grid. These early wells also intersected several coal seams, which became a primary drilling target for the first time in 1998 when a well was drilled and then cavity stimulated. The first two production pilots, which were drilled between 1998 and
2006, targeted the Bohena Coal Seam with fracture stimulated vertical wells. The wells flowed at commercial rates, in the order of 150 Mcf/d gas and 150 bbl/day water, confirming the prospectivity of the area for coal seam gas. In 2006 the current titleholder recognized that the permit had greater potential for coal seam gas than conventional petroleum and since then work has focused exclusively on coal seam gas targets.
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