Oil and gas field development is a complex comprehensive project consisting of exploration,drilling,downhole operation,oil recovery and transportation.A large number of chemicals are used in every link of the operation.In recent years,the global drilling workload has continued to increase,with more than 110,000 wells drilled worldwide in 2012.Drilling is undoubtedly one of the most important tasks in oil exploration and oilfield development.
The products of CD Chemical Industry for drilling industry are:1.Potassium formate as excellent drilling fluid and completion fluid;2.Sodium tripolyphosphate as drilling mud dispersant;3.Sodium hexametaphosphate as anti-rust of drilling control pipe and control of viscosity of mud during oil drilling.
Potassium formate,as a drilling fluid and completion fluid with excellent performance,is widely used in oil field industry.Its action mechanism has four main points:
(1) Ion exchange:potassium ion can replace sodium ion in montmorillonite to form stable structure which is not easy to expand and disperse.
(2) Lattice immobilization:Potassium ions are embedded in the voids formed by oxygen atom grid between adjacent layers of illite,forming bonds,thus limiting the expansion and separation of adjacent layers.
(3) Charge neutralization:The high ion concentration in potassium formate solution can compress the electric double layer of clay colloid particles,which greatly weakens the negative electricity of clay and reduces the hydration expansion capacity.
(4) Low activity:The addition of potassium formate will reduce the free water in drilling fluid,resulting in a certain osmotic pressure difference,which is conducive to preventing pressure transmission to shale,thus inhibiting the hydration expansion and dispersion of shale.
The solubility of many salts in potassium formate solution is very low.By adding potassium formate solution,high density and low viscosity can be achieved,drilling speed can be improved and drill bit life can be prolonged.However,potassium formate solution can better dissolve alkaline earth metal sulfate and its sodium chloride.When potassium formate solution is used in salt or gypsum formations,it will collapse or poor cementing quality.Therefore,special attention should be paid to the effect of potassium formate concentration and temperature on the solubility of sodium chloride and calcium sulfate.