A new generation Wireline Formation Tester (WFT) was used to perform fluid sampling in a subject field as part of an appraisal drilling campaign targeting significant undeveloped conventional oil reserves. The field consists of free gas caps with associated saturated oil intervals that appear as thin rims around anticlinal flanks. Resistivity log analysis predicated a mud filtrate invasion volume of 89L. Approximately 150% of the expected invasion volume (128L) was pumped during sampling. Laboratory results showed that the sampled fluid was still mud filtrate, despite pumping an extra 50% of the estimated volume required for hydrocarbon breakthrough. This paper presents a mathematical model for predicting filtrate invasion and post drilling WFT cleanup performance. A new methodology is developed to incorporate critical shear stress concepts into mud filter-cake thickness and filtrate invasion calculations. The mathematical model is used to provide input data for Eclipse reservoir simulator (E100) and an analysis of the field case. The model can also be applied as a predictive tool for filter-cake development, filtrate invasion and pump-out volumes required during fluid sampling. In addition, the model can be used to design optimal mud properties that minimize filtrate invasion and extra treatment of the invaded zone post-drilling. The mathematical model is integrated with reservoir simulation to model the cleanup process. The mathematical model developed in this study predicted an invasion volume of 528L, which is significantly greater than what was estimated based on resistivity logs (89L). This implies that filtrate invasion volume in the field case was underestimated. A sensitivity study showed that filter-cake permeability was the greatest determinant of filtrate invasion volume, and that radius of filtrate invasion was the greatest control on mud filtrate cleanup during sampling. Reservoir simulation provided a good match between model simulation results and field data.

Over the past few years, there has been a surge of interest in using Australia's coalbed methane (CBM) resources to produce liquefied natural gas (LNG) for export, taking advantage of increasing prices and growing global demand for gas. Principally in Queensland, the second largest state, situated in the northeast of the country, there has been significant investment by a number of companies to secure footholds in this resource play. By December 2008, seven proposals for LNG plants had been announced, most involving partnerships between Queensland companies with coal seam gas resources and international petroleum companies. Most exploration and appraisal CBM wells are tested to determine pressures and coal seam deliverability. As the majority of wells cannot flow to surface naturally, closed chamber tests are conducted, most often in open hole. An alternative testing method employed by a number of operators in Australia over the past 2 years has been the dual packer module of wireline formation testers. Although wireline packers provide a cost-effective and an efficient way of obtaining high-quality pressure transient data sets, they are limited to relatively small test intervals. A new, innovative approach enables testing coal seams of up to 15 m in thickness using wireline formation testers. The new wireline formation testing configuration offers several benefits over conventional drillstem tests (DST) for this application, including rig-time savings. Another benefit of the new technique is the broad range of drawdown and inflow rates, extending coverage from very low- to high-permeability coals. Additional applications used in the field include step-rate tests, the results of which have been applied to assess and rank different coal seams across a number of fields and coal types.

A coal seam gas (CSG) to liquefied natural gas (LNG) project in Queensland, Australia, has an active exploration and appraisal program in support of future development activities. Critical to exploration and appraisal is the evaluation of permeability, skin, and reservoir pressure. Drill stem testing (DST) has been the most common form of evaluation since the inception of the industry in Queensland over the last 10 years. DSTs commonly used in the CSG industry are modified ‘slug’ tests in which a water cushion provides hydrostatic backpressure on the formation to reduce the likelihood of gas break-out and two-phase flow. Although DSTs have become an industry-accepted method for evaluating permeability, skin, and extrapolated reservoir pressure, there are some disadvantages to this approach. A new wireline formation testing technique addresses the evaluation objectives of CSG testing in the Surat and Bowen basins. In addition to efficiency and cost-effectiveness, the approach provides additional testing flexibility; this includes the ability to manage a broad range of drawdown and inflow rates, extending its applications from very low to high permeability coals. Additional applications include step-rate tests, across both the Walloon coal measures of the Surat basin and the Bowen basin's Bandanna formation.

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.