Implementation of Wireline Formation Testing Configuration for the Evaluation of Coal Seam Gas Plays in Surat and Bowen Basins in Australia

Pourabed, Hamid Reza; North, Tim; Harfoushian, Jack

doi:10.2118/167082-ms

Cited by 4 publications

References 8 publications

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Magnetotelluric monitoring of coal seam gas depressurization

2016

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The depressurization of coal seam gas formations causes in situ fluids to migrate through pores and fractures in the earth. The removal or discharge of large volumes of water from coal measures reduces in situ fluid pressure allowing natural gas to be released from the coal matrix. This process results in a time-dependent resistivity variation in the subsurface. Increasing the connectivity of in situ fluids may lead to a reduction in resistivity of the targeted lithologies. A correct assessment of such resistivity variations is of significant interest not only for the industry to optimize production and extraction well locations but also for the regulatory bodies, in which a desire for a reliable method for monitoring changes in subsurface fluid distribution allows sound risk assessment of potential environmental hazards. From an industrial field study conducted in Queensland, Australia, we have found that the magnetotelluric (MT) method in the bandwidth of 100 Hz to 100 s could be used to monitor changes in the bulk resistivity of depressurized lithologies. Results from our study indicate the orientation of fluid flow resulting from depressurization, which can be mapped and directly attributed to spatial and temporal variations in permeability. The MT method is introduced as a low-cost, low-impact technology that can be used for short- and long-term environmental monitoring.

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Magnetotelluric monitoring of coal seam gas depressurization

2016

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A New Approach for Efficiently Evaluating Highly Permeable Coalbed Methane Reservoirs in Surat Basin, Australia

Pelling

Thorburn

Pourabed

et al. 2014

SPE Annual Technical Conference and Exhibition

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Following the first commercial recovery of coal-seam gas (CSG) in the 1990s, the CSG industry in Queensland has grown rapidly due to the abundant reserves (~33 000 PJ) and global demand for LNG. There are currently three LNG export projects under construction on Curtis Island near Gladstone in Queensland, with the first shipment scheduled for middle to late 2014. In preparation for the completion of the first LNG plant, the QCLNG project, operated by QGC, is currently ramping up CSG production in the Surat basin. By the end of 2014, more than 2000 wells will be drilled and connected to the QGC gas-and-water-gathering network, and thousands more are scheduled for drilling and completion in subsequent years of the project. To meet the production target, it is increasingly important for QGC to accurately evaluate the well productivity during the early stage of development to optimise the operation of the field and ensure all LNG contractual agreements are met. To date, drillstem testing (DST) has been the most common form of evaluating CSG well productivity. However, the improved capabilities of the wireline formation tester (wireline FT) for testing larger coal intervals (between 1 and 15 m) and deriving similar reservoir parameters is making it a popular alternative to the more costly DST. Nevertheless, although facing very few issues in low-permeability coal seams, the wireline FT is unable to create sufficient pressure drawdown in higher permeability coal seams (>100 md) due to the mechanical limit of its downhole pump (<20 B/D). As a result, the wireline FT interval pressure builds up to formation pressure rapidly and stabilises to gauge resolution within the first few minutes. This causes significant uncertainty in the permeability measurement. In view of these wireline FT limitations, operators have been more inclined to evaluate the higher-permeability coal intervals with DST services, therefore motivating wireline service providers to find ways of improving wireline FT capability This paper describes utilising super flow technique to create sufficient drawdown in highly permeable coals using wireline FT sample chamber module. Superflow simulates closed-chamber DST by using the high volume sample chamber module of the wireline FT tool. Two different superflow techniques have been implemented with positive results. Several superflow tests were compared with conventional drawdown/build-up tests over a number of coal intervals of varying permeability to confirm the validity of the new testing method. The results indicate this technique has extended the wireline FT capabilities to higher permeability coals that have been typically conducted by DST services. The addition of the sample chamber module and corresponding superflow theory, the wireline FT has broadened the range of CSG applications.

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A Probabilistic Approach to Predicting Coalbed Methane Well Performance Using Multi-Seam Well Test Data

Burgoyne¹,

Clements²

2014

SPE Asia Pacific Oil &Amp; Gas Conference and Exhibition

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Significant heterogeneity in production rates from coalbed methane (CBM) wells is observed throughout the Surat and Bowen Basins in Eastern Queensland, Australia. Typically, individual well performance predictions are conducted using deterministic coal properties obtained from core data in combination with permeability and pressure measurements from multi-seam well testing. Due to the heterogeneous nature of the coal, the total permeability measured across the tested interval in a single well will likely not represent the behaviour of even the closest of neighbouring wells. This leads to challenges in mapping permeability between and away from wells, and producing representative predictions for field development. A new method is proposed to take a statistically significant population of multi-seam CBM permeability test results, correct to equivalent expected single seam test results and, using the full dataset, relate those results to a probabilistic single well performance envelope for a defined area with similar geological properties and setting. Depth, gas content, saturation, total net coal isopachs and any unique structural features are the primary control points for defining these ‘geodomains’. The resultant single well performance envelopes remove the need to subjectively choose an average permeability to use for each well or coal measure. The results have been demonstrated to reasonably represent the range of observed actual peak water and gas productivities across a variety of geological areas in the Surat and Bowen basins. This provides a method by which discrete representations of well families can be made for a particular geologic setting; leading to an understanding of the range of potential well outcomes which cannot be achieved using a typical deterministic approach.

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Implementation of Wireline Formation Testing Configuration for the Evaluation of Coal Seam Gas Plays in Surat and Bowen Basins in Australia

Cited by 4 publications

References 8 publications

Magnetotelluric monitoring of coal seam gas depressurization

Magnetotelluric monitoring of coal seam gas depressurization

A New Approach for Efficiently Evaluating Highly Permeable Coalbed Methane Reservoirs in Surat Basin, Australia

A Probabilistic Approach to Predicting Coalbed Methane Well Performance Using Multi-Seam Well Test Data

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