Abstract Measurements on hydrate-bearing laboratory and field samples are needed to provide realistic bounds on parameters used in the numerical modeling of the production of natural gas from hydrate-bearing reservoirs. These parameters include thermal conductivity, permeability, relative permeability-saturation relationships, and capillary-pressure-saturation relationships. We have developed a technique to make hydrate-bearing samples, ranging in scale from core-plug-size to core-size, in the laboratory to facilitate making these measurements. In addition to pressure and temperature measurements, we use x-ray computed-tomography (CT) scanning to provide high-resolution spatial data providing insights on location-specific processes occurring in our samples. Computed tomography allows us to better attribute measured quantities to locations where processes occur and not to the bulk sample. Several methods are available to make gas hydrates in the laboratory, and the method impacts the behavior of the test sample and the parameters measured. We present CT data showing hydrate saturation in samples, and thermal conductivity of laboratory-made samples estimated using the inversion code iTOUGH2 for samples with known and unknown hydrate distributions. Knowledge of the hydrate distribution greatly improves the interpretation and confidence in property measurement.

Abstract X-ray computed tomography (CT) is an established technique for non-destructively characterizing geological cores. CT provides information on sediment structure, diagenetic alteration, fractures, flow channels and barriers, porosity and fluid-phase saturation. A portable CT imaging system has been developed specifically for imaging whole-round cores at the drilling site. The new system relies upon carefully designed radiological shielding to minimize the size and weight of the resulting instrument. Specialized X-ray beam collimators and filters maximize system sensitivity and performance. The system has been successfully deployed on the research vessel JOIDES Resolution for Ocean Drilling Program’s legs 204 and 210, at the Ocean Drilling Program’s refrigerated Gulf Coast Core Repository, as well as on the Hot Ice #1 drilling platform located near the Kuparuk Field, Alaska. A methodology for performing simple densiometry measurements, as well as scanning for gross structural features, is presented using radiographs from ODP Leg 204. Reconstructed CT images from Hot Ice #1 demonstrate the use of CT for discerning core textural features. To demonstrate the use of CT to quantitatively interpret dynamic processes, we calculate 95% confidence intervals for density changes occurring during a laboratory methane hydrate dissociation experiment. The field deployment of a CT represents a paradigm shift in core characterization, opening up the possibility for rapid systematic characterization of three-dimensional structural features, and leading to improved subsampling and core-processing procedures.