Electrical anisotropy of gas hydrate-bearing sand reservoirs in the Gulf of Mexico
- 作者：Ann E. Cooka ; acook@ldeo.columbia.edu ; Barbara I. Andersonb ; John Rasmusc ; Keli Sunc ; Qiming Lic ; Timothy S. Collettd ; David S. Goldberge
- 关键词：Gas hydrate saturation ; Electrical anisotropy ; Sand reservoirs ; Gulf of Mexico
- 刊名：Marine and Petroleum Geology
- 出版年：2012
- 期刊代码：37_02648172
- 类别：pw
- 出版时间：June, 2012
- 卷：34
- 期：1
- 页码：72-84
- 文件大小：936 K
摘要
We present new results and interpretations of the electrical anisotropy and reservoir architecture in gas hydrate-bearing sands using logging data collected during the Gulf of Mexico Gas Hydrate Joint Industry Project Leg II. We focus specifically on sand reservoirs in Hole Alaminos Canyon 21 A (AC21-A), Hole Green Canyon 955 H (GC955-H) and Hole Walker Ridge 313 H (WR313-H). Using a new logging-while-drilling directional resistivity tool and a one-dimensional inversion developed by Schlumberger, we resolve the resistivity of the current flowing parallel to the bedding, R鈥?/sub> and the resistivity of the current flowing perpendicular to the bedding, R鈯?/sub>. We find the sand reservoir in Hole AC21-A to be relatively isotropic, with R鈥?/sub> and R鈯?/sub> values close to 2 惟 m. In contrast, the gas hydrate-bearing sand reservoirs in Holes GC955-H and WR313-H are highly anisotropic. In these reservoirs, R鈥?/sub> is between 2 and 30 惟 m, and R鈯?/sub> is generally an order of magnitude higher.
Using Schlumberger鈥檚 WebMI models, we were able to replicate multiple resistivity measurements and determine the formation resistivity the gas hydrate-bearing sand reservoir in Hole WR313-H. The results showed that gas hydrate saturations within a single reservoir unit are highly variable. For example, the sand units in Hole WR313-H contain thin layers (on the order of 10-100 cm) with varying gas hydrate saturations between 15 and 95%. Our combined modeling results clearly indicate that the gas hydrate-bearing sand reservoirs in Holes GC955-H and WR313-H are highly anisotropic due to varying saturations of gas hydrate forming in thin layers within larger sand units.