|Borehole Tool for the Comprehensive Characterization of Hydrate-bearing Sediments
||Last Reviewed 12/1/2015
The project goal is to conduct a review of hydrate-bearing sediment properties and the inherent effects of in situ sampling for the purpose of designing, developing, and field-testing a new borehole tool to comprehensively characterize hydrate-bearing sediment in situ.
In Phase 1 of the project, researchers will review and update the database of hydrate-bearing sediment properties at Georgia Tech in order to develop robust correlations with index parameters. The resulting information will be incorporated into a tool for optimal field characterization. The design will recognize past developments, build on past characterization experience, and benefit from inspiring examples from nature and other fields. In Phase 2, researchers will design the tool’s electronics and instrumentation, construct a full-scale prototype, and initiate laboratory testing on hydrate sediment analogs. Finally, in Phase 3 the borehole tool will, in collaboration with industry, be deployed in the field to characterize both hydrate-bearing and hydrate-free sediments.
Georgia Tech Research Corporation, Atlanta GA 30332
While earlier research focused on the properties of the hydrate mass per se (Sloan Jr and Koh 2007), studies during the last decade have increasingly explored hydrate formation in both marine and permafrost sediments, their properties (Santamarina and Ruppel 2008; Waite et al. 2009), and production strategies. Reservoir simulators require reliable material parameters to anticipate reservoir response and production rates. Hydrate saturation governs initial properties and gas recovery; strength and stiffness before and after dissociation determines the deformation field and stability conditions; liquid and gas permeabilities and their variation with saturation define flow rates; and heat capacity and conduction limit dissociation.
The study of methane hydrate-bearing sediments currently relies on wireline logging or sampling. Logging while drilling (LWD) and measure while drilling (MWD) provide valuable information, but material properties required for analysis and design are inferred through correlations. On the other hand, sampling permits direct measurement of properties but faces pronounced challenges due to sampling disturbance followed by inherent difficulties with core handling and testing under pressure/temperature stability conditions.
Inherent sampling disturbance presents the greatest challenge to geo-analyses and engineering production strategies. Drilling, wall shear, core recovery, specimen extrusion from the sampler, and trimming and insertion into test chambers produce sediment “destructuration” and have a pronounced effect on all sediment properties (Baligh et al. 1987; Hight et al. 1992; Hvorslev 1949; La Rochelle et al. 1981; Ladd and DeGroot 2003; Landon 2007; Santagata and Germaine 2005; Santagata and Germaine 2002; Shogaki and Kaneko 1994). Furthermore, classical recompression techniques often considered in hydrate-free sediments will not reproduce the original stress–strain conditions when sampling alters the sediment structure, as is expected in all unconsolidated sediments (Tanaka 2000; Tanaka et al. 2002). The sources of sampling disturbance that affect hydrate-free sediments affect hydrate-bearing sediments as well. The presence of hydrates aggravates sampling effects (even when pressure core technology is used) due to pressure- and temperature-dependent hydrate dissolution and dissociation and time-dependent hydrate relaxation. A new borehole tool for characterizing hydrate-bearing sediments in situ will help researchers avoid the inherent difficulties and biases in sampling sediments, which are exacerbated when sampling hydrate-bearing sediments.
The proposed research reflects a convergence of multiple favorable conditions including sensor miniaturization,the availability of extensive data gathered from multiple laboratory and field studies, and past experience in characterizing hydrate-bearing sediments. The proposed sampling tool and characterization methodology will have profound impacts in the field such as:
- Direct measurement of sediment properties in situ to avoid sampling disturbance
- The most comprehensive site characterization tool for characterizing hydrate-bearing sediments
- The ability to robustly and reliably determine sample characteristics in situ complemented with pre-existing knowledge and post-sampling lab characterization (when plugs are recovered)
- A characterization tool and approach designed to provide information needed for reservoir simulations and analysis tools used for resource recovery, seafloor stability studies, and environmental evaluations
Such information plays a critical role in the design of strategies for resource recovery, seafloor instability analyses, and environmental studies.
- The penetration and soil sampler modules were successfully tested in shallow beach sand sediments in Lake Acworth, Georgia.
- The first prototype of the downhole tool was designed and constructed.
Current Status (December 2015)
Researchers continue to design and build modules for the first prototype of the downhole tool. A major development was the redesign of electronics to improve the robustness of the operation. Due to the amount of sensors and the limited space in the body to house the controllers, researchers decided to add a new component: a Raspberry Pi microcontroller. This controller can act as a master controller and two Arduino UNO will be the slaves. Therefore, the Arduino UNO will be the direct connection to the sensors and save the data in SD cards. The master will communicate with the Arduino when to operate and will keep the clock running (for sampling purposes).
In order to avoid delays in field operations researchers are constructing a total of three in-situ tools. The tools will allow the testing of three different operating modes: (1) full stand alone (no communication with the surface, (2) wired for real time data gathering and operation, and (3) a hybrid operation mode which allows customization according to the application.
Physics-inspired models are being developed to provide robust predictions of the properties of hydrate-bearing sediments, taking into consideration pore habit. These models are guided by physical principles and are anchored to experimental observations and data.
During the next quarter the team has tentative plans for a test deployment of the tool in the Red Sea. Researchers have developed plans with the Red Sea Research Center (KAUST, Saudia Arabia) to run the first series of tests on near-surface sediments at incremental water depths.
Project Start: October 1, 2013
Project End: September 30, 2016
Project Cost Information:
Phase 1 – DOE Contribution: $138,944; Performer Contribution: $39,980
Phase 2 – DOE Contribution: $176,572; Performer Contribution: $41,979
Phase 3 – DOE Contribution: $161,509; Performer Contribution: $44,078
Planned Total Funding – DOE Contribution: $477,025; Performer Contribution: $126,037
NETL – Skip Pratt (firstname.lastname@example.org or 304-285-4396)
Georgia Tech Research Corporation – Carlos Santamarina (email@example.com or 404-894-7605)
Quarterly research Performance Progress Report [PDF-395KB] July - September, 2015
Quarterly Research Performance Progress Report [PDF-625KB] October - December, 2014
Quarterly Research Performance Progress Report [PDF-4.17MB] July - September, 2014
Quarterly Research Performance Progress Report [PDF-2.39MB] April - June, 2014
Quarterly Research Performance Progress Report [PDF-1.11MB] January - March, 2014
Quarterly Research Performance Progress Report [PDF-545KB] October - December, 2013