Fremgangsmåte for å fjerne filterkake fra vegger i et borehull

摘要

Well drilling and servicing fluids for use in producing formations to deposit filter cake therein comprise water, a density increasing water soluble salt, a fluid loss control agent, a hydratable polymer solid suspending agent and a particulate solid bridging agent which is soluble in an aqueous ammonium salt solution. The deposited filter cake is then contacted with an aqueous solution of an ammonium salt to dissolve the bridging agent.