Experimental Study of Sand Production during Depressurization Exploitation in Hydrate Silty-Clay Sediments

Abstract

Silty-clay reservoirs are a weak point in sand production and sand control studies due to their low economy. However, China’s marine natural gas hydrates (NGH) mostly exist in silty-clay sediments, which restrict the sustainable and efficient development of NGH. In order to study the sand production of hydrate silty-clay sediments, hydrate production experiments in vertical wells and horizontal wells were carried out using a self-developed hydrate sand production and sand control simulation device. The results showed a great difference between the hydrate silty-clay sediments and hydrate sand sediments. The significant differences in production pressure and production temperature between the different layers indicated the low permeability and low heterogeneity of the hydrate silty-clay sediments. The sliding settlement of the overall depression in the horizontal well and overall subsidence in the vertical well of the hydrate silty-clay reservoir would easily lead to silty-clay flow and large-scale sand production. When water rates decreased, the property of “silty-clay sediment filtration and wall building” was found, which formed a “mud cake” around the wellbore. The good strength of adhesion and fracture permeability of the “mud cake” provided ideas for reservoir reformation. This study further discusses sand production and sediment reformation in hydrate silty-clay sediments.

Effect of Permeability on Hydrate-Bearing Sediment Productivity and Stability in Ulleung Basin, East Sea, South Korea

“…In the first field production test of the Mallik project in 2007, the production period was only 1.5 days due to the occurrence of sand production [10]. Sand production can lead to production well clogging, and excessive stress concentrated around the production well can cause the well to collapse [43]. Therefore, in future studies, productivity and stability analyses that consider the effects of sand production are required.…”

Enhancing Gas Production from Hydrate-Bearing Reservoirs through Depressurization-Based Approaches: Knowledge from Laboratory Experiments

“…The temperature in this figure refers to the temperature of the reservoir after the formation of hydrates. Data shown are from refs , , , , , , , , , , , and .…”

Sand production behaviors during gas recovery from sandy and clayey‐silty hydrate‐bearing sediments: A comparative analysis

“…After hydrate dissociation (for about 32 min for sandy GHBSs; 110 and 90 min for clayey-silty GHBSs when saturation was 20% and 30%, respectively), the temperature increased very slowly due to the exchange of heat with the surroundings. 20,29,31 For all samples, the outlet pressure decreased from 10 to 0.1 MPa within 40 min. However, owing to the different characteristics of samples, the inlet pressure showed different depressurization characteristics.…”

“…12 The subsidences in the vertical and horizontal wells of clayey-silty GHBSs would easily lead to mudflow and large-scale sand production, and a mud cake would form around the wellbore with the water production rate decreasing. 20 The tests on samples from the Liwan area of the Northern South China Sea also reported that very fine silt GHBS was prone to sand production. 21 The experimental work mentioned above focused either on sandy or clayey-silty GHBS separately, which are unable to be compared directly due to the different conditions of the experiments.…”