Prediction And Control System Technology Of Wellbore Hydrate In Gas Field Production System

At present, China conducted a large-scale shale gas exploration and development. But as key technology is still in a backward state, the majority of working wells can’t fit our expectation. As the initial extraction pressure is very high, production process can easily generate hydrate, and high pressure process on the ground need stricter requirements. It is necessary to depart from the overall gas production systems, from the wellbore began to hydrate prediction and prevention of work to do, simplified process flow downstream system, reducing the overall production system harm hydrates. Therefore, the study of gas hydrate prediction and prevention measures has practical significance.This article is based on a shale gas field production GY block production systems hydrate prevention issues as the research object, the use of down-hole choke manner to achieve the purpose of prevention of hydrate in the whole production system. The type of gas hydrates, as well as the nature of the formation mechanism and conditions is briefly outlined, and hydrate control measures are described, comparing the advantages and disadvantages of the method steps for the subsequent production system hydrate control measures choose a clear direction. Then on the production site commonly used to predict hydrate empirical fitting method and scientific research from different angles to generate a prediction made by the model are described briefly discusses the principles and methods applicable to each model. Describes the concept and principle of down-hole throttling technology in gas field production systems prevention hydrate derived un-throttled wellbore pressure and temperature distribution model, temperature and blood pressure drop model down-hole choke and throttle wellbore temperature and pressure distribution determined section flow processing parameters design process.Briefly introduced PIPESIM software calculates the required flow and pipe flow correlations. With PIPESIM and then the actual data flow to production wells correlations were fitted, preferably suitable for the production of blocks GY Hagedorn & Brown correlations. PIPESIM through the use of simulation software to multiple factors that affect the sensitivity of hydrate formation were analyzed and discussed the influence of different factors on the production of hydrate formation in the wellbore. Last conclusion:(1) Restrictor diameter is smaller, the greater the voltage drop across the orifice, the lower wellhead pressure, corresponding to the hydrate formation temperature is lower, the less conducive to hydrate formation. The smaller the diameter of the mouth, the more obvious the throttling pressure drop, wellhead pressure drop, the more beneficial to prevent hydrate formation;(2) Low formation pressure, wellbore temperature and pressure curve of hydrate formation curve has no intersection, indicating no hydrate formation. With the formation pressure decreases, keeping yields under the same circumstances, to the bottom of the wellhead pressure decreases, the corresponding hydrate formation temperature drops below the wellhead temperature to avoid hydrate formation there;(3) Gas production and reservoir pressure constant wellbore pressure of different diameters different variations. Under conditions of different diameters, to the bottom of the wellhead same temperature, but the larger diameter, the greater the pressure differential in the production process, to lower wellhead pressure. So meet the production requirements of the conditions, use a larger diameter, to avoid hydrate formation.(4) The wellhead pressure gradually reduced and the wellhead temperature was gradually increased with the increase of gas production. Gas production changes has little effect in gaswell production, but the greater the gas production, the better to avoid hydrate formation.By un-throttled and throttled gaswell were simulated to predict hydrate formation position, preferably throttling process parameters, compared to fewer than at the throttle and the throttle gas production when, demonstrated by the design parameters effectiveness. Prediction error simulation results with the actual production data between the smaller, indicating that the design is feasible.Finally the actual site design and simulation applications, the use of on-site PIPESIM occur hydrate frozen block wells design, system simulation of simple production wells and gathering branch line consisting of analysis, design parameters of down-hole choke in maintaining with production requirements, select 4.5mm diameter restrictor mouth down into the depths of 1500m wells to combat the wellbore and the wellhead generated hydrate.Through the designing from the perspective of the whole production system field of view, the use of downhole throttling technology, can effectively control gas hydrate problems in GY block.