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Multi-scale Investigation On Gas Production Of Class ? Hydrate Reservoir By Depressurization

Posted on:2022-04-24Degree:MasterType:Thesis
Country:ChinaCandidate:X H HuangFull Text:PDF
GTID:2481306509483804Subject:Energy and Environmental Engineering
Abstract/Summary:PDF Full Text Request
Natural gas hydrate is considered as a new energy with great commercial development prospect because of its huge reserves,clean and pollution-free.According to the reservoir conditions and geological characteristics of hydrate reservoirs,hydrate reservoirs can be divided into four classes.Among them,Class I hydrate reservoir is composed of overlying hydrate layer and underlying free gas layer and is seemed as “hydrate-capped gas reservoir”,which is the most economical exploitation value of the four classes hydrate reservoirs.Because Class I hydrate reservoir has multiple layers with different properties,the interlayer heat and mass transfer and interaction between hydrate layer and free gas layer are complex.At present,there is still a lack of systematic research on the influence of heat and mass transfer and interlayer interaction on gas production process,which affects the design and analysis of the high efficiency exploitation scheme of Class I hydrate reservoir.In this paper,the experimental and numerical simulation study on producing Class I hydrate reservoir by depressurization is carried out from the laboratory scale and the field scale,respectively.By changing the filling mode of sand and water,the experimental study of Class I hydrate reservoir by single well depressurization is carried out.The temperature,pressure and gas flow rate are monitored when producing by depressurization,which provided material and verification basis for the follow-up numerical simulation.Based on the experimental data,a laboratory-scale numerical model is constructed to analyze the effect of interlayer interaction on gas production behavior.The results show that gas produced in the early stage is mainly the free gas in free gas layer,while in the later stage gas production rate is controlled by hydrate decomposition rate.Therefore,the hydrate layer can be used as caprock to prevent gas leakage in the early stage and as gas source to increase gas production in the later stage.In addition,the effects of different intrinsic permeability and initial hydrate saturation on gas production behavior are analyzed.The results show that higher intrinsic permeability can shorten the production cycle,and higher initial hydrate saturation hinders the production of free gas in the early stage but significantly increases the gas production in the later stage.Combined with the numerical model verified by experiment and field geological exploration data,a numerical model for Class I hydrate reservoir by depressurization production in the South China Sea is established.Three production well locations(free gas layer,hydrate-gas layer and hydrate layer)are designed and their production performance is discussed.The results show that when the production well is located in the hydrate layer,the gas production is the highest,but it is accompanied by high water production,large formation disturbance,obvious secondary hydrate formation and other adverse phenomena.In addition,the production performance evaluation of Class I hydrate reservoir is closely related to the permeability variation characteristics.Different permeability prediction models have complex gas and water production characteristics.Therefore,reservoir characteristics,production economy and safety should be taken into consideration when designing the efficient exploitation scheme of Class I hydrate reservoir.
Keywords/Search Tags:Class I hydrate reservoir, Depressurization, Laboratory scale, Field scale
PDF Full Text Request
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