生物酶增效DTPA螯合剂解除重晶石堵塞的机理与性能OA

When drilling low-temperature geothermal wells into high-pressure formations,the barite(BaSO4)in weighted drilling fluids,under the action of differential pressure,invade formation fractures and form insoluble filter cakes to block flow channels,causing production capacity to reduce.Regular acid job measures cannot be used to effectively dissolve barite,thus chelating blocking removing agents composed mainly of aminopolycarboxylates(such as diethylene triamine pentaacetate,DTPA)become a potential solution.Using DTPA as the main agent,the effects of reaction temperature,concentration of the main agent,bioenzyme(α-amylase)and basic conversion agent(K2CO3)on barite dissolution were systematically investigated.The performance of the blocking removing agent was evaluated through filter cake dissolution test and scanning electron microscopy(SEM),and the working mechanism was revealed.The results show that:(1)the dissolution capacity of DTPA solution for barite increases with increase in temperature.At 65℃,the optimum concentration of DTPA is 15%;adding 0.5%α-amylase and 4%K2CO3 on this basis can synergistically improve the dissolution effect,and an optimum blocking removing formula(15%DTPA+0.5%α-amylase+4%K2CO3)was then obtained,with barite dissolution capacity of 35.3 g/L.(2)The results of SEM analyses demonstrate that the barite particles after treatment exhibit porous and fracturing morphology,with roughness significantly increased.Filter cake dissolution experiment confirms that this blocking removing agent can efficiently penetrate into,dissolve and disperse barite filter cakes.Mechanism studies reveal that DTPA dissolves barite synergistically by inducing lattice distortion and chelating.(3)An index of"solute ratio"is presented to characterize the efficiency of removing barite from the borehole wall.The solute ratios in different boreholes are all greater than 1,indicating that the blocking removing agent can effectively remove filter cake attached to the borehole walls in a single treatment.The achievements made in this research provide a technical reference for reservoir protection in low-temperature geothermal well drilling.