New Tailored Spacer System Helps Reduce Lost Circulation and EnhancesCement Bonding during Multistage Cementing Operations in FracturedFormations in Kyumbinskoe Field,Eastern Siberia

摘要

Lost circulation(LC)is commonly encountered in drilling and cementing operations and can significantlycontribute to non-productive time(NPT).An operator in the Kyumbinskoe Field faced this challenge ina fractured production section of the formation,and conventional LC solutions had been ineffective atachieving strict regulatory top of cement(TOC)requirements and satisfactory cement bonding.This paperdescribes a tailored spacer fluid system engineered to effectively and efficiently prevent LC to meet thejob requirements.The tailored spacer system includes additives that perform synergistically to help preventLC in permeable and fractured formations and enables rheological hierarchy to facilitate effective muddisplacement.The spacer was designed to meet operational parameters for cementing a production casingstring in two stages through the use of a multi-stage tool and was subjected to thorough verification throughlab testing and computer simulations to ensure job requirements could be met.The tailored spacer systemwas used in three trial jobs to assess its ability to minimize losses in a permeable and fractured formationwith a history of LC with the ultimate goal to achieve planned TOC and improve cement bond quality asverified by Cement Bond Logs(CBL's).Use of this tailored spacer system helped to minimize losses experienced on all three wells.CBL resultswere also significantly improved with an average of 70% of the cemented interval being classified as"good bond"on wells cemented without the tailored spacer system to 88% on the three wells where it wasused.Barrier dependability with the new spacer system was improved through achieving strict regulatoryrequirements for TOC on two out of three wells and improved cement evaluation results,which is a criticalrequirement of well construction that allows for maximizing production over the life of the well.