Research On Gas Production Key Technology Of The Xujiahe Formation In Central Sichuan

Xujiahe formation distributed widely in Sichuan Basin,which mainly contains massive sandstone with second,fourth and sixth segments of large scale and deep thick river-delta system.Xujiahe formation is an important development block of Southwest Oil&Gas Field with the estimated reserves of natural gas up to 35542×108m3.However,the gas wells for this reservoir always has the characteristics of low natural productivity,large water production and difficult liquid-carrying capability,which affect the gas wells normal production.This paper focus on the low cost and high efficiency purpose,combines theory and practice,physical simulation and field tests,hardware and software to study multi-layered/multi-staged technology of horizontal wells,low cost gas production and work over technology,the main work completed is as follows::(1)According to reservoir geologic characteristics,a set of low molecular,slippery water and fluid jet fracturing fluid system was developed;Indoor study shows that the proppant added with fiber concentration at 1.5 percentage to 2 percentage can effectively prevent sand output,the dosage of resin-coated proppant at 15 percentage to 20 percentage can efficiently prevent proppant from flowing back.(2)In order to realize the layered and segmented stimulation of reservoir,this paper also have developed composite bridge plugs with ? 114.3mm(42/2")?? 127mm(5")??139.7mm(51/2")series(temperature resistance up to 120?,differential pressure up to 70MPa),basically formed composite bridge plug operation technology,and good field application results have been achieved.Hydraulic jet downhole tools was developed,and this paper also put forward a jet fracturing optimization design method toward construction capacity,nozzle number and the scale of construction.(3)To solve the problems of downhole throttle in water producing wells,such as difficult to fishing fixed downhole throttle,throttle damage for sand production by fracturing treatment,mobile throttle rubber has weak condensate resistance,this study has improved the fishing head structure and choke of fixed downhole throttle,made optimum selection evaluation for mobile downhole throttle rubber,and changed the rubber cup to rubber sleeve to improve the fishing efficiency.Based on self-built two-phase choke experiment platform,gas-liquid two-phase choke experiments have been carried out.Additionally,the author also have revised tradition two phases choke relations,enhanced design accuracy of downhole throttle for gas and water producing wells and improved basic theory of downhole throttle technique for gas and water producing wells.(4)According to the characteristics of formation water with high salinity and Ba2+,and condensate in Xujiahe gas reservoirs,we have developed foaming agent-CT5-7c?.Laboratory experiments and field test results indicate that this newly developed CT5-7C?foaming agent can be applied in Xujiahe formation of central Sichuan,and perfect effect have been achieved.(5)For the field application problems by introducing overseas plunger gas lift systems,we have independently developed plunger downhole clamp,intelligence plunger and plunger controller,and finally achieved remote controlling and transmission of plunger operating parameters,which give the important basic data support to plunger gas lift operating system optimization.(6)For the Xujiahe formations in Central Sichuan always have the characteristics of strong water sensitivity,acid sensitivity and certain degree of water lock damage,we firstly propose snubbing operation safety control technique,have developed matching tubing plug,and improved the relevant basic theory,which give the important technology support to effectively develop Xujiahe formation in Central Sichuan.Through the study toward reservoir stimulation,downhole throttling,gas recovery by liquid drainage and workover technology in Xujiahe group gas reservoir,this paper has formed a set of recovery technology which is low-cost but very efficient,provides powerful technical supports for the improvement of recovery efficiency and the achievement of low-cost and efficient development.At the same time,it also provides valuable reference to the development of similar gas field in China.