In drilling mud,solids particles more than 15microns have big influence to mud performance and machinery drilling speed,its percentage of all solids is about 70%.People strive to remove them with effective machinery equipments.Along with the development of drilling technology,the requirement is higher to mud performance.Practice has proven the solids control to improve the mud performance is a essential drilling mud aided technology which can keep the borehole conditions and promote the drilling speed. In order to provide the premium mud,it’s necessary to outfit a complete suitable mud cleaning system, this is a guarantee to keep the drilling mud performance excellent.
According to the usage of solids,The solids particles in drilling mud are divided two categories:
1.Useful Solids,such as bentonite,barite,chemicals treatment agents,etc.
2.Unuseful Solids,such as drilling cuttings,inferior bentonite,sands,etc.
Drilling fluids solids control is for removing harmful solids and keeping useful solids to meet the requirement drilling technology to drilling fluids performance.
Generally,drilling fluids solids control is called in short Solids Control.
The importance of solids control is receiving the attention,it’s the essential factor to influence safe、excellent、high-effective drilling and protection of oil&gas reservoir.It’s one of the important means to achieve drilling optimization.Doing solids control well can provide necessary conditions to scientific drilling.Correctly proceed to do solids control can protect oil&gas reservoir,decrease the torque and friction,reduce the pressure fluctuation of annulus suction,lower the probability of differential pressure sticking,enhance the drilling speed,lengthen the service life of drilling bit,alleviate the abrasion of the equipments and pipes,increase the wearing parts’ work-life in drilling fluids recycling system,increase the well bore stability for improving the conditions of running casing,alleviate the environment pollution,reduce the cost of drilling fluids etc.The statistics data at work-site shows that in the range of low density,the solids content in drilling fluids reduce per 10% (equivalently drilling fluids density reduce 0.01),generally the drilling speed can improved about 8%. It proved the effectiveness after doing solids control well is very significant.
Oilfield Drilling Mud Cleaning System |
The exist of unuseful solids in drilling fluids is the biggest hidden danger to destroy the drilling mud performance,decrease the drilling speed then lead to various complex underground circumstance.Through the long term practice and continuous research,people concluded the adverse influence of the high content unuseful solids to drilling works are below:
1. In drilling mud,high content solids,the special gravity will increased,differential pressure at the bottom of well will largen,enhanced the “chip hold down effect” of the liquid column to rock,these are disadvantageous to rock crushing at the bottom of hole.High content solids will decrease the ability to bring the drilling cuttings,large number of big solids particles cann’t be discharge out of hole make the bit crush rock again and again,hence increase the drilling tools’s wearing and influence the drilling speed.
2. During the process of drilling,water loss of drilling fluids and content of solids particles influence the quality of mud cake on the well wall.Small drilling fluids water loss,mud cake is thin and tough,protecting well wall better are our goal.High content solids particles, drilling mud water loss increased make the shale formation sucked water,hydration swelling, hole wall instability,cause the drill down poor,induced the hole accident.Besides,the mud cake is thick and loose will make the drilling tools are adhesive with well wall then induced the sticking accident.
3. More solids particles,more machinery abrasion to recycling system,more abrasion to cylinder sleeve,piston,then the maintain time will be increased and lead to the drilling efficiency lowed.High content solids will generate the scaling in the inner wall of drill pipe hence influence the inner pipe salvage and be forced to handle the scaling and break off the normal drilling procedure.The efficiency of drilling exploration also be lowed since the increased aided works.
4. In the process of drilling,due to the drilling cuttings enter into the drilling mud,if the solids cann’t be removed timely,the drilling mud performance will be changed.When the content of the sands in drilling mud is more than 4%,the drilling mud will be regarded as waste mud,it’s necessary to discharge the waste mud and change the new mud.Most drilling mud belong to alkaline solution,discharged randomly will destroy the plants,alkalify the soil,affect the plants regenerated.In addition,some additives in drilling mud make the mud turn black,if discharged a lot,it will generate the vision pollution.
At present,there are 4 methods to decreasing the solids content in drilling mud.
1. Drilling mud is diluent with clear water.
2. The mud in the well is changed with clear water and new drilling mud.
3. Solids subsided under their own gravity in tank.
4. Purified with mechanical equipments.
Generally,the first and the second methods are proceeded at the same time.