| Shale gas is a kind of natural gas which is rich in organic matter,mature dark mud shale or high carbon mud shale,because of the adsorption of organic matter or the existence of cracks and matrix pores in rock,which makes it store and preserve the biological origin,pyrolysis origin and their mixed origin of certain commercial value.Compared with conventional natural gas,the reservoir of shale gas reservoir is generally characterized by low porosity and low permeability.usually,the permeability is less than 1×10-3?m,the highest porosity is only 4%?5%,and the airflow resistance is larger than that of conventional natural gas,so it is necessary to implement reservoir hydraulic crushing before mining.The current fracturing methods are:multistage fracturing,water fracturing,synchronous fracturing,hydraulic injection fracturing,repeated fracturing and so on.The function of the surface fracturing wellhead device is to connect the surface fracturing vehicle set with the oil casing string in the wellbore,so that the fracturing fluid pumped from the fracturing vehicle through the wellhead is pumped into the underground shale strata to reach the fracturing target.At the same time,the fracturing fluid will be discharged back to the ground through the fracturing wellhead.Therefore,the pressure bearing capacity of wellhead device,the switching flexibility and sealing ability of wellhead valve directly affect the selection of fracturing fluid pump volume and surface fracturing limit pressure,and the confirmation of return velocity.The core assembly of fracturing wellhead is ball screw valve for fracturing,the performance of which determines the effect of fracturing operation.Large-caliber shale gas fracturing in order to ensure the pump volume of fracturing fluid,it is necessary to choose the big pass valve,and the working condition of super high pressure?general pressure is 70Mpa,105Mpa and above?,which makes the valve switching torque of conventional plate structure more than 500N.m,which cannot guarantee the requirement of field operation.In order to make the field switching become easy to operate,and in case of emergency,the personnel can cut off the well head through the control system outside the dangerous area of the well head,a large-caliber remote control hydraulic valve is designed.The gate valves specified in this design calculation are designed and manufactured according to the requirements of the petroleum and natural gas industry standards and API Spec6A specifications,and mild corrosion resistant materials are selected as components of oil and gas wellhead installations and various pipe sinks containing sulfur oil and natural gas.Fracturing process requires that the valve has the characteristics of light operation,reliable seal,round channel,small flow resistance,long life,simple and compact structure,good manufacturing process,low cost and so on.In addition to meeting these requirements,the gate valve can also meet the bidirectional flow of the medium,and when the full open or closed state,the closing part is less eroded by the medium.Therefore,reliable work can be guaranteed under high pressure.Through design calculation and design stress analysis,it is verified that the product meets the requirements of API Spec 6A specification,and the process verification,function and performance verification are carried out on the basis of sample trial production. |
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