Drilling fluid is a circulating washing medium in drilling explore. Drilling fluid is the blood of drilling also called drilling hole washing fluid. Drilling fluid can be divided into pure water, mud, no clay phase flushing fluid, emulsion, foam and compressed air. Pure water is the earliest drilling fluid, it need not dispose and easy to use, it adapts the complete stratum and enough water area. Mud is the widely used drilling fluid, it is mainly adapts to loose, fracture, easy to collapse, it meets water will swell and the hole wall unstable stratum.
In drilling process we can accord the change of ground drilling mud to know the bottom well condition.
The change of drilling fluid viscosity
Abnormal increase: if it is the fresh water maybe meet the gypsic horizon, salt paste layer. We should contact stratum drilling teams at times to know the stratum, taking the right measures and ensure the project is safety. If it is the salt mud or calcium treated mud, maybe meet the loose soft stratum, we should increase the Macromolecule polymer content in drilling fluid and increase drilling fluid density.
First rise after descent; maybe meet the salt stratum or salt water stratum, we should stop drill, cyclic adjustment the performance of drilling fluid, firstly increase viscosity and decrease loss water increase drilling fluid density balanced stratum pressure.
Viscosity is decreased: maybe drill to the high pressure salt water stratum, we should increase viscosity and density, pressuring steady salt water stratum and ensure under well is safety.
Viscosity is increased the foam is increased: we should stop drill and check at times. We should check drilling fluid filtrate chloride root content and contact drilling teams. If the chloride is increase and the high pressure is unusual which indicating drill to the oil gas level. if the chloride is normal and drilling fluids performance is instability maybe drill to CO2 gas level, we should increase drilling fluid density and eliminate CO2.
The viscosity is increase and the colour is black and has offensive smell indicate that drill to the hydrogen sulfide formation, we should stop drill at times, increase drilling fluid density and add caustic soda.
The change of drilling fluid density
Density is decrease: maybe drill to the oil gas level or water level, appearing the oil gas invade or water invade, we should stop drill at times and circulate aggravate and balance stratum pressure.
Density is increase: indicate that aggravate is too big or drilling cuttings invade to the mud, we should start centrifuge and other solid control equipment, decrease drilling fluid density can meet the requirements of drilling. Adjusting drilling fluid sticky cutting, it also can meet the requirements of well mouth purification.
Mud loose water is increase
The mud maybe is polluted by calcium or salt, we should treatment to the mud at times and increase the capacity of mud resistance salt and calcium pollution.
The change of mud PH
Decreased: maybe drill to CO2 or H2S and other acid gas stratum, we should increase the density at times and pressure steady the useless gas and add the caustic soda or basic zinc carbonate treatment agent and recovery PH, maintenance the system is steady and ensure bottom well is safe.
Increased: it maybe drill to cement plug. The mud is polluted by calcium, we should eliminate the calcium and recovery system performance.