Research On Drilling And Completion Technology Of Geothermal Wells In Rongcheng Area,Hebei

The Rongcheng area of Hebei is rich in geothermal energy and the thermal reservoir is shallowly buried,which has high mining value.However,the formation of the water intake well section in this area is complex,and accidents such as borehole instability are prone to occur.Secondly,in order to ensure the higher water outlet temperature,high cementing quality are required.The average drilling cycle is about 875 hours,which severely restricts the development of local geothermal energy.Therefore,in view of the geological characteristics of the Rongcheng area in Hebei,optimizing the drilling and completion technology of geothermal wells is of great significance to the subsequent construction of geothermal wells.Using magnetotelluric sounding to invert the resistivity equivalent section and the stratigraphic boundary section,and compare the adjacent well and actual drilling logging data,determine the depth of the interface between the Minghuazhen Formation and the Jixian Formation,and determine the technical casing depth.The prediction range can be accurately within 10 m to ensure the safety of construction.The clay shale hydration mechanics coupling simulation experiment device and the elongated strain gauge are used to measure the hydration stress,and the influence of temperature,aqueous solution and other factors on the hydration stress is analyzed.Amino silanol is used as a clay shale inhibitor.Compared with the small cation inhibitor CSW,the hydration stress is reduced by 26.7%.The micro-drilling method is used to determine the rock drillability grade of thermal reservoirs.According to the rock drillability grade,refer to the drill bit manufacturer’s recommended model to determine the drill bit model.In view of the geological characteristics of thermal reservoirs in Rongcheng area,a well completion method of water filter pipe+blind pipe+water stopper production is formulated,which can effectively prevent geothermal water from flowing to non-producing layers and prevent clay shale wall from falling into the wellbore,reduce the impact on the effluent discharge.Based on the analysis of the main factors of cementing quality,the cementing technology is proposed to prevent channeling and improve the displacement efficiency measures.It adopts shortening the thickening time of cement slurry and increasing the effect of‘right angle thickening’to overcome the cement slurry‘weightlessness’during the freezing period,causes water channeling in the annulus.The Landmark software was used to simulate the centering of casings with different numbers and types of centralizers when the inclination angle was greater than 40°,so as to use the centralizers reasonably and improve the casing centering.By improving the regularity of the well diameter and optimizing the performance of the drilling fluid,the overall pressure balance and efficient displacement are realized to ensure the efficiency of cement displacement.The optimized drilling and completion technology measures were applied to the field test wells.The drilling cycle was shortened by 74 hours,the wellhead water output was 115 m~3/h,and the wellhead water temperature was 54℃,which met the mining requirements.The depth of the interface between the Minghuazhen Formation and the Jixian Formation was accurately judged,used to determine the technical casing depth to provide guarantee for subsequent construction.Amino silanol drilling fluid was used to effectively inhibit clay shale hydration without well wall collapse and other complex conditions.When cementing the method of injecting cement slurry with density difference was used to realize double solidification,shortened the thickening time by 40 minutes,realized the overall pressure balance and high efficiency displacement with the turbulent return velocity of 1.0-1.4 m/s,and improves the cementing quality rate to 83.5%,which has a significant effect.