A Research On Temporary Plugging-divertion Of Acid Fracturing In Tahe Oilfield

Compared to the main region,Tahe low-quality carbonate formations have less natural fracutres,complex oil-water relationship,and vast reserve.Horizontal wells with mostly open hole completion are the common production method to develop such formations.Staged acid fracturing with packer plus slide sleeve in open hole horizontal wells has problems such as long cycle,operation compolexity,poor reliability of tools,and difficulty to fishing the tools left in the hole.A new technology of staged fracturing without using tools has been applied to this oilfield.Aiming at this technology,this thesis do a research on temporary plugging additive evaluation,optimization of temporary plugging parameters,and field applications.The thesis is mainly based on experiment research,combined with analytic analysis and numiercal simulation.Fistly,do high-temperature rheological experiment to evaluation performance of gel acid and crosslinked acid systems commonly used in the field.Next,with broken cores for simulation of natural fractures,acid core flooding is conducted to evaluate the performance of ceramisite,degradable fiber,and degradable particle.The amount of the additives are optimized by a series of core flooding.Then,a series of core flooding are conducted for evaluating performance of composite temporaryplugging additives and optimizing the parameters of the combination.Finally,the technology of staged fracturing without tools is applied to the field.Optimized paramters in the experiment are scaled to reservoir conditions.Pump schedule design and parameter optimization in acid fracturing are accomplished with Fracpro PT.The study shows that single type of plugging additive with crosslinked acid system can generate up to 7MPa diversion pressure.For ceramsite,100-mesh ceramsite has a better performance,and 3.0g addition is recommended in the experiment coditions,the concentration of which is 3.0%.For degradable fiber,5mm is recommend,and optimized addition is 3.0g in the experiment conditions,the concentration of which is 3.0%.The addition of degradable particle is recommended 3.0~4.0g,the concentration of which is 3.0%~4.0%.Combination of single plugging additive has better performance than a single additive.Combination of big balls,fiber,and small particle with equal fraction results in good plugging effect,the concentration of which are all 1.0%.Big balls can plug larger vugs,fibers bridge fractures and interwine plugging additives to provide stable support,small particles fill small pores.Composite plugging agent can create up to 15 MPa pressure,which is much higher than typical fracturing pressure difference of 5~9MPa.The field applications validated the effectiveness of the staged fracturing without tools.This research provides basis,fundamental data,and optimized parameters for staged fracturing without tools,and is of significance for the development of lowquality carbonate formations in Tahe oilfield.