Australian reservoir laboratory provides integrated shale services

The Australian oil and gas industry is positioning itself as a significant global LNG supplier with massive investments occurring on both the eastern and western coasts of the continent. The developments in western parts are propelled by production from a small number of highly complex deepwater wells.

In contrast, the developments in eastern Australia rely on thousands of wells to exploit relatively shallow coal seam gas (CSG). By creating a new lucrative market, the developments in the east also have energized the exploration and appraisal activity, spurring operators to redevelop existing plays and explore new ones, especially the unconventionals.

Although the offshore and unconventional projects on these two coasts vary dramatically in their physical characteristics, all of them require improved reservoir understanding to efficiently and safely extract the valuable contents.

The rugged environment, complex geology and limited amount of reservoir knowledge make shale oil and gas recovery both a challenge and an opportunity. Unconventional resources display extreme variability in rock composition and post-deposition diagenetic processes.

FIGURE 1. The laboratory relies on a three-pronged approach to help operators better understand unconventional reservoirs. (Source: Schlumberger)

Operators must quickly and efficiently locate reservoir sweet spots and identify well landing locations to recover hydrocarbons at economically viable levels. Core and fluid analysis services play an important role in improving knowledge of shale reservoirs and, ultimately, unlocking reserves in areas such as the Cooper Basin, where the understanding of complex and heterogeneous reservoirs is critical.

Reservoir characterization lab opened

Schlumberger recently opened a reservoir characterization laboratory in Brisbane to address the needs of Australian oil and gas operators through comprehensive rock analytical services for offshore and onshore operations, including the rapidly growing shale and CSG activities.

The facility combines field and laboratory analytical capabilities starting with sample acquisition, laboratory measurements on reservoir core and fluids, interpretation and modeling services, and providing recommendations to operators. This approach saves operators valuable time and costs by capturing core at the well site, preparing samples, managing the project, and analyzing and interpreting the data.

The timely delivery of accurate reservoir characterization information is essential in reducing projects’ risk, simplifying operations and improving field productivity.

A key component of the service capabilities rests with the company’s petrotechnical experts, who are available to provide actual simulations and results based on the core analyses. Whether the challenge is calibration of a mechanical earth model for hydraulic stimulation or a validation of gas-in-place estimations from the core analysis, they can develop a complete solution including logging program design, core analysis test program, model development and log calibration.

Laboratory overview

The new laboratory is one of the few facilities in Australia that has advanced rock mechanics testing capabilities. Previously, the local industry relied on universities, research laboratories and overseas facilities to fulfill their testing and analysis needs. Depending on the size and complexity of the project, rock mechanics testing could take up to 12 months to complete. Now operators have a local and timely alternative.

To better understand unconventional reservoirs, a three-prong workflow is used for the quantification of heterogeneity, measurements of reservoir quality and completions quality (Figure 1). All of these rock measurements complement fluid characterization measurements obtained in the Brisbane laboratory and the global network of Schlumberger Reservoir Laboratories (SRLs). The network has the capacity to conduct analyses of fluid properties and integrate rock and fluid data for full reservoir characterization.

In a recent example, the laboratory delivered test results to a customer in Australia within five weeks of wellsite operations. This rapid turnaround enabled the operator to be better informed as work progressed.

The facility has its own geomechanics testing equipment. The laboratory houses tri-axial rock mechanics machines. Computer-controlled and designed to simulate in situ stress and strain, these machines help determine physical properties of geotechnical core samples.

FIGURE 2. An N-dimensional HRA of logs and high-resolution, continuous strength profiles along the core length are used to select the samples for laboratory testing to ensure that all of the different rock units of the core are adequately represented. (Source: Schlumberger)

The test systems simulate actual in situ conditions and characterize a test sample's behavior under these conditions. Axial load, pore pressure and a confining pressure to create horizontal stress can all be precisely controlled. In-vessel instrumentation, directly in contact with the rock sample, accurately measures the sample's response to testing variables.

In addition, specialized core analysis equipment available through SRLs accurately measures reservoir rock petrophysical properties such as porosity, permeability and saturations. For unconventional reservoirs, this equipment uses both pressure and pulse decay methodologies to measure properties of tight rocks.

Geoscientists and petroleum engineers from across the organization serve as global subject matter experts. Specialists in nanodarcy to microdarcy permeabilities contribute specific unconventional core expertise.

Also, the laboratory collaborates with Queensland University of Technology to broaden regional capabilities and research efforts, particularly in enhancing CSG production. Together, the organizations investigate challenges such as thin coal seams and stimulation methods as well as development opportunities of unconventional Australian resources.

While the laboratory addresses regional operators’ needs, it also leverages the specialized capabilities of other SRLs. Through these network facilities, the Brisbane laboratory provides special core analysis, including relative permeability, nuclear magnetic resonance and electrical properties in addition to reservoir fluids analysis such as composition and phase behavior.

Geomechanics, core analysis

The laboratory provides extensive rock mechanics testing capabilities for land and offshore operations and also core analysis for unconventional reservoirs. Operators evaluate geomechanical properties to understand wellbore stability during well construction and reservoir depletion during the production phase.

Pore volume compressibility and depletion measurements help operators anticipate signs of subsidence in maturing fields. For unconventional onshore operators, shale core analysis, for example, assists in hydraulic fracturing stimulation and well placement decisions required to optimize reservoir production.

Sample selection is critical to ensure reliable and representative results. Even small differences between predicted and actual texture, mineralogy or fluid saturations can affect tight shale gas producibility. For this reason, the laboratory offers the heterogeneous rock analysis (HRA) service, a log interpretation technology that identifies different rock classes as part of the sampling strategy.

Operators also can use the HRA service in conjunction with rotary sidewall plug sampling in tight gas shales and other wildcat wells. A well-designed rotary sidewall plug plan identifies a sufficient number of representative samples to evaluate reservoir sections and their heterogeneity adequately.

Laboratory experts work closely with the other specialized teams to conduct petrophysical and geomechanical studies in a timely manner. A geomechanics study to reduce wellbore problems during drilling and enhance the completion design for a major Australian operator was completed in less than half the time a previous supplier had required.

Integrating fluid, core analysis services

The technology skills and experience to integrate the measurements performed in the laboratory include the propagation of results and solutions to a wellbore scale. This is known as core-to-log integration. The HRA plays a key role in the core-to-log integration serving as a robust platform that identifies different lithologies and provides a sampling strategy to optimize the characterization of reservoirs in the laboratory setting (Figure 2). The HRA is used for all formation types, though it is most often used for unconventional reservoirs where the material properties change the most.

Finally, integration of fluid and core data is vital for the enhancement of hydrocarbons production in shale plays. Not only are the fluids analyzed but also the rock properties that enable the reservoir producibility. The integration of results from both fluid and rock properties strengthens the services of other experts who provide wireline logging, drilling, completion and well stimulation treatments.