Gas Fields In West Hydrate Control Technology Research

At frigid winter and spring prime season,gas wells of Western Sichuan Gas Field probably form the gas- hydrate,which block up production facilities and gathering pipeline,it reduce well startup time and seriously affect regular production of gas wells. At the moment, Western Sichuan Gas Field mainly take production control means and high-pressure grid gas scavenging line method to prevent gas hydrate blockage in wellbore and gathering line sepatately,many problems are still remains: harming reservoir,affecting gas production,existing potential safety hazard and increasing gas consumption.For effectively prohibiting the hydrate blockage of gas wells,which have complex well course or dirty inner wall tube,or longer production period and whcih have high-pressure. This article do the application of basic researches of alcohol injection and downhole throttle technology respectively.In theory the main research workes have done as follows.1) Based on deeply analysesing the thermodynamics behavious of hydrate formation, using the Du-Guo Model to compute the gas-hydrate generation condition for pure water system. Apply highly accuracy Jafar Javanmardi Model to predicte the hydrate formation temperature to giving pressure for inhibiters system(electrolyte and alcohol),but no flash calculation algorithm is needed for electrolyte system,which can be suit for the conditon containing high solubility gas ingredients,for example: carbon dioxide and hydrogen sulfide.2) This article establish temperature and pressure prediction models of wellbore and surface pipeline,which consider the heat transfer process between borehole and layer when calculate pressure and temperature distribution of entire borehole,using Ramey-Willhit's wellbore heat transfer model to compute the overall heat transfer coefficient.While placing the bean choke in the wellbore,on the foundation of performance analysis for critical choke flow process, suitable model can be seek to compute the choked pressure and temperature droping values.3) Applying mathematics fitting means of the gas saturated moisture chart,and combining Hammerschmidt empiric equation to calculate minimum inhibitor's concentration in liquid phase,the appropriate inhibitor usage model can be presented,using it to design the alcohol injection parameters.Through relational expression between gas flow rate and choke diameter and heel-and-toe choke pressures under critical flow condition, calculation formula of choke diameter can be derived. According to designed well flow rates and SWHP,on the ground of temperature-pressure model based on wellbore radial thermal conduction,coupling hyrate formation condition and gas temperature after choking,this article build the new calculation method of choke setting depth,which suited to Western Sichuan Gas Field.Using Visual Basic 6.0 software to compile computer programs for forementioned theorise and methods.In engneering applications,based on the analysis of production characteristics of Western Sichuan Gas Field, this article make alcohol injection and downhole throttle technology parameters designs and site applications of four gas wells.Doing the alcohol injection technological designs for LianYi 101 and 105. Comparing the inhibitory effect and economic benefit of methanol or glycol.,methanol(industrial alcohol)be taken as execution medicament,and detailed construction scheme be maken.Through the downhole throttle technological designs of ChuanXiao 452 and MaPeng 43 to deeply study the it's adaptiveness and technological process,and do some research on the factors such as setting depth of choke and wellhead pressure,which effect wellhead temperature after choking.The four gas wells keep up persistent producing pressure and gas flow rate after practising this two hydrate prevention measures,which demonstrate that alcohol injection or downhole choke technology can effectively prevent hydrate blockage, guarantee regular production of gas well and improve economic benefit.