Since 2007, Guangzhou Marine Geological Survey (GMGS) is leading multiple drilling campaigns to confirm the occurrence of in-situ natural gas hydrate in South China Sea. Multiple expeditions had been carried out in the following years to quantify gas hydrate and to determine the nature and hydrate distribution within the sedimentary sequence. To achieve these objectives, GMGS utilized LWD logging data as primary means to identify gas hydrate bearing zone, followed by coring and sampling in selected locations.
This paper discusses the petrophysical evaluation of gas hydrate using extensive LWD data acquired in Shenhu area incorporating high-resolution image data. This includes utilizing resistivity spectrum analysis to quantify formation heterogeneity and applying sand counting analysis for better gas hydrate saturation estimation in heterogeneous strata. Moreover, gas hydrate occurrence mode identified by resistivity image corresponds well with cores collected from hydrate bearing zone. Resistivity image is also used to analyze hydrate accumulation sequence, formation model and provides valuable information in gas hydrate controlling factors assessment in this area.
Under scrutiny as one of the new energy sources that could help satisfy global energy demand after the success of shale gas, gas hydrate represents an alternative source of natural gas waiting to be exploited. Although there are many studies trying to quantify gas hydrate reserves worldwide, the actual quantity is still poorly defined till now. U.S. Geological Service (USGS) estimates the natural gas hydrate worldwide to be twice the amount contained in all fossil fuel on Earth including coal (Collett, 2001), but most technologies associated with regards to gas hydrate production is still at an early stage of development.