Research and application of micro-foam drilling fluid in Daqing Oilfield

Micro-foam drilling fluid has advantage comparing with conventional water-based drilling fluid in such aspects as protecting oilgas layer and leakproof,especially suitable for low pressure and yield reservoir in Daqing Oilfield.Foaming agent and foam stabilizer are screened out which translates present well drilling fluid system into micro-foam drilling fluid system.Micro-foam drilling well fluid formula,suitable for micro-foam exerting function,whose properties such as inhibition,temperature resistance and antipollution(anti-clay,calcium and oil and gas) ability,oil layer protecting effect(simulation core dynamic pollution test) and anti-sloughing mechanism and rheology character of micro-foam well drilling fluid as well are researched,is established.And specific rheology model of micro-foam well drilling fluid is established.Plugging mechanism of micro-foam well drilling fluid is researched by API well drilling fluid water loss and leaking stoppage experiment and API leaking stoppage material experiment.It shows that micro-foam well drilling fluid has lower fluid density,which can reduce shaft liquid column pressure to mitigate well leakage,is of good lubricity,small circulating pressure loss and low pump pressure,which reduces circle equivalent density of well drilling fluid.High viscosity and shearing stress properties of micro-foam well drilling fluid increase flow resistance of well drilling fluids in fractures and pores,which is good for stopping continuous emergence of well loss.Micro-foam coalescing but binding in fractures and pores has bridging plugging effect,which stops continuous flow of well drilling fluid in leaking-out channel.Field application shows that micro-foam well drilling fluid can reduce oil layer pollution resulting from drilling and improve well productivity.