Latex Flexibilizer For Oil Well Cement Prepared By Miniemlusion Polymerization

The quality of well cementation is a key factor of oil-gas well lifetime andrecovery efficiency. Currently, oil-gas-water channeling and interfacial cementationproblem occur frequently in domestic well cementation engineering, one of the reasonfor this is the brittleness of cement stone. During the later exploitation, somemeasures, such as perforation, fracturation and acidification, can bring impact andvibration to cement stone, and lead to brittle fracture of cement stone. Thereby, theinterfaces between cement stone and drive pipe or side wall would be damaged andthe zone isolation function would be lost. Thus, the addition of flexibility reagents tocement slurry is of great meaning to improving the oil-gas lifetime and recoveryefficiency, due to the fact that this kind of materials can lower the brittleness ofcement stone and bring it some plastic deformation ability.In this paper, styrene-butadiene latex used as a flexibility for oil well cement wasprepared through miniemlusion polymerization with styrene(St) as hard monomer,liquid polybutadiene with low molecular weight ?LPB? as soft monomer and2-acrylamide-2-methlpropane sulfonic acid (AMPS) and acrylic acid(AA) asfunctional monomers. The latex was used as a flexibilizer for oil-gas cement. Resultfrom infrared spectrometer(IR) shown that all monomers participated in thecopolymerization. Transmission electron microscopy(TEM) was used to observestructure and distribution of latex particles, results shown that the particles had acore-shell structure, the diameter was about120nm and in uniform distribution.Thermogravimetric analyzer was used to characterize the thermal stability of thepolymer, result shown that the polymer hardly decomposed below320?, the heatresistant was excellent.After mixture of latex and cement, we studied the general performance,compressive strength, breaking strength, water loss and thickening property of thelatex-based cement according to the testing of oil well cement GB/T19139-2003.Results shown that: the latex-based cement slurry remained stable, no thickening wasobserved after curing; the fluidity was much better than pure cement slurry, free fluidwas0; the compressive strength and breaking strength were improved and flexibility was greatly enhanced; water loss was less than50mL, thickening curve presentedright angle thickening, transient time was short, and the ability of gas channelingprecaution was excellent, all these facts together indicated that cement slurry with thelatex prepared by us could meet the cementing engineering requirements well.