Environmentally-Friendly Fluid Foss Additive For Oil-based Frilling Fluids Development And Performance Evaluation

Oil-based drilling fluids have the advantages of high temperature resistance,resistance to salt and calcium intrusion,favorable for maintaining borehole stability,excellent lubrication,and less damage to oil and gas layers.They are used for drilling complex wells such as deep wells,multi-lateral wells,and high-angle directional wells,horizontal wells and have played a huge role.Today’s stringent environmental laws have prompted the use of bitumen oil-based drilling fluid systems that urgently required an efficient and environmentally-friendly fluid loss additive.In this paper,acrylamide（AM）and maleic acid（MA）as functional monomers,ammonium persulfate as initiator.Polymer MA-AM was prepared by inverse microemulsion polymerization,and then Fourier infrared,laser particle size distribution and scanning electron microscopy were used to characterize the morphology of MA-AM.PSD experiments show that the polymer fluid loss additive has a good hydration film and deformability.SEM show that the particle size is 70-150 nm,and has a normal distribution.Through a series of experiments,it was found that MA-AM possesses strong adhesion,good drop filtration,and can achieve the best results at a 1%increase,indicating that MA-AM is a good fluid loss agent of oil-based drilling fluid.Subsequently,the basic performance of the MA-AM oil-based drilling fluid was tested,and the density limit of the MA-AM oil-based drilling fluid system was2.2g/cm³,the rheological properties of the oil-based drilling fluid were good within the density limit,and the maximum demulsification voltage was reached 975V.And experiments found that MA-AM oil-based drilling fluid system has a good temperature resistance at 190°C.By testing the luminescent bacteria inhibition rate,chemical oxygen demand,and biochemical oxygen demand of the MA-AM,it was confirmed that the 1%concentration of MA-AM had a luminescence inhibition rate of 1.1%,and the ratio of BOD₅/CODcr was 0.38.Therefore,MA-AM has a good environmental affinity and solves the problem of large environmental damage caused by asphalt-based fluid loss agents.This proves that MA-AM is a fluid loss additive with excellent environmental protection and fluid loss.