It Is Suitable For The Research And Field Application Of Cementing Fluid System In Yongye Block

Shale gas is a high-quality,clean and efficient unconventional natural gas resource.Yongchuan development block is an important area of shale gas in China.In order to meet the requirements of shale gas drilling and development,the wellbore structures of this area are mostly horizontal wells,long sealing and long horizontal section,multi sets of drilling fluid systems are usually used.This research is carried out in order to meet the requirements of corresponding cementing engineering and cementing working fluid system.According to the composite of metal ionic polymer commonly used in the drilling fluid system and diesel-based drilling fluid system,two different flushing fluid systems of drilling fluid systems suitable for this block are developed as follow:water+8%HSCXJ+0.5%SXP-1,and the corresponding flushing efficiency is 95%;water+15%HSCXJ+2%special fiber+0.5%SXP-1,and the corresponding flushing efficiency is 93%.Because of the high formation pressure coefficient in Yongchuan shale gas development block,The weighted isolation fluid system suitable for cementing in Yongchuan shale gas development block is designed as:water+3%HSGLJ+0.5%SXP-1+X%TFJZJ;The weight dosage of agent changes in the range of 1.30?1.80g/cm3;The settlement stability is good;The density difference is less than 0.04g/Crr13;Water loss is less than 30mL;The rheology and temperature resistance are excellent;All the above mentioned properties fit the performance requirements of cementing engineering in Yongchuan shale gas development block.Considering the unstable performance of fluid loss agent used in cementing in Yongchuan shale gas development block,a fluid loss agent with a suitable molecular structure is synthesized by studying the performance impact of fluid loss agent with different monomer ratio,reaction time,reaction temperature,initiator concentration and so on.The optimum scheme of SZ is as follows:The monomer molar ratio is LY:AA:AM=45:20:35;Reaction temperature is 50?;Reaction time is 3 hours;Initiator concentration is 1.5%.The result of infrared spectroscope shows the structure of polymer.The thermogravimetric analysis shows that the temperature resistance of SZ can reach at 260?.The performance study shows that while the dosage of SZ is 4-6%,API water loss can be controlled within 50 ml in the range of 45?-150?,which means SZ has good ability of water loss control and temperature resistance.For improving the cementing property and long-term integrity of cement in this block,The compatibility of the synthetic fluid loss agent and the common cement slurry admixture is studied,and the high cementing expansive cement slurry system suitable for the second drilling cementing in Yongchuan shale gas development block is obtained:JHG+4.0%SZ+0.3%SXY-2+3.0%SEP-2+0.3%SXP-l+44%H20;The density is 1.93g/cm3;The 48h relative expansion rate is 1.5%;API water loss is 40 ml;The thickening time is adjustable,and other parameters are all good enough.Based on the high cementing expansive cement slurry system suitable for second drilling cementing,the high-elastic(plastic)expansion cement slurry system suitable for the third drilling cementing in shale gas development block is obtained:JHG+4.0%SZ+0.3%SXY-2+3.0%SEP-2+2.0%WG+0.3%SXP-1+4.0%STX+44%H2O;The elastic modulus is 6.67GPa;The density is 1.92g/cm3;The thickening time is adjustable,and other parameters are all good enough.The compatibility of flushing fluid,isolating fluid,drilling system and cement slurry system are studied.The results show that the compatibility of four fluids mentioned above is good.The ratio of thickening time of working fluid system with varying proportion is more than 1.0,and the thickening curve is smooth and stable.The cementing working fluid system studied in this paper is completely suitable for cementing engineering in Yongchuan shale gas development block.The cementing fluid system consisting of flushing fluid system,isolating fluid system and cement slurry system is tested in Yongchuan 3 and 6 wells.According to the geological conditions of the second drilling and the use of composite metal ionic polymer drilling fluid system,a cementing fluid system is designed:flushing fluid+isolating fluid+expansive cement slurry system.The double-setting time expansive cement slurry system is adopted,and the cementing section is about 3500 M.The two wells represent good cementing effects of 89.5%and 91.5%respectively.In view of the need for multi-stage fracturing in the process of shale gas development and the use of diesel-based drilling fluid system in the third drilling,the cementing fluid system of the third drilling is designed as:flushing fluid+isolating fluid+flushing fluid+elastic(plastic)slurry system.The double-setting time cement slurry scheme is adopted and the whole well section is sealed,the two wells achieved good cementing effects of 94.8%and 96.8%respectively.The cementing fluid system studied in this paper represents high cementability,high elasticity(plasticity)and temperature resistance.It has achieved good results in the test of Yongchuan shale gas development block field,and it has a good prospect and value in the further application.