Research On Environmentally Friendly Oil-based Drilling Fluid Viscosity Increasing Agent

The shale gas exploration and development is the hot spot in the current oil and gas industry,shale gas development in SiChuan area has entered a boom in recent years.In the shale gas development process,due to shale formation hydration expansion,coupled with complex geological of shale gas reservoir structure in our country and high incidence of downhole accident,using oil-based drilling fluid can protect the oil production and solve these problems very well.However,oil-based drilling fluid used in practical application,because of its relatively high economic costs and the use of long carbon chain synthetic base crude,which will result in excessive oil content of drilling cuttings and make a bad impact on environment.So the study of oil-based drilling fluid to reduce costs and pollution is of great significance.Analyzed the development situations of oil-based drilling fluid and the drilling tackifier,this paper synthesis an oil-based drilling fluid tackifier,named aluminum phosphate.Diesel oil-based drilling fluid formulated by the drilling tackifier and low cost diesel,improved the traditional oil-based drilling fluid formula.The common clay is better hydrophilic than organic soil,so it can reduce the oil content of drilling cuttings.By orthogonal designs,changing the time,temperature,materials ratio and other reaction conditions to explore the optimal reaction conditions.Using triethyl phosphate and phosphorus pentoxide as raw materials to synthesize polyphosphate intermediates,then generated phosphate intermediates with the mixtures of n-decanol,n-octanol,lauryl alcohol and n-hexyl alcohol,and finally the aluminum salt was added,a aluminum dialkyl phosphate was synthesized.The chemical structure was characterized by IR.The drilling tackifier has the advantages of simple preparation process,shorten the gelation time,reduce the cost,a good cisvosity-shearing improving capability.Its resistance temperature can reach 90 ?.Based on the optimization of the oil-based drilling fluid,the diesel oil-based drilling fluid with the tackifier were successfully prepared.It has good suspending ability,emulsion stability and low filtration.After a middle temperature aging,The rheological properties,electrical stability and filtration of drilling fluid system are all stable.The density of drilling fluid has little effect on plastic viscosity and dynamic filtration.It shows that this diesel oil-based drilling fluid suitable for the development of shale gas within 2000 meters,the density can be selected based on actual conditions on site,to meet the basic requirements of oil-based drilling fluid.The effects of demulsifier dosage,demulsifier concentration,demulsification temperature,demulsification time,rotate speed and centrifugal time on the thermo-chemical demulsification and centrifugal separation of the emulsion were investigate.The oil content of drilling cuttings was tested.The oil content of drilling cuttings in diesel oil-based drilling fluid is lower than in white oil-based drilling fluid,and the oil content can reach the emission standard of environmental protection.