Study On Control Targets For Suspended Matter And Oil Content Of Injected Water

As for oilfield flooding or sewage reinjection system, oil content and suspended matterin injected water also refer to the main factor of descending water absorbing capacity inwater injection formation apart from one of the important control target of injected waterquality index. Therefore, how to determine the applicable index for oil content andsuspended matter by combining specific reservoir has always been the difficult point in waterquality standard of water injection development oilfield.This thesis studies the damage of concentration and different suspended matters inmedian particle size to permeability of formation core by applying quantitative filtermembrane to adjust size distribution of on-site sewage and adopting the method of coreflowing test simulation. It is indicated by results of indoor core flowing test that whenphysical characteristics （length, diameter, gas permeability and porosity） of the core areroughly close, the larger median particle size and particle concentration of suspended matterare, the larger the created permeability losses will be; when the concentration of suspendedparticle is certain, the larger median particle size is, the larger the created permeability losseswill be; it can be reflected by core permeability damage experiment of an oil productionplant that when the permeability damage is set within15%, as for formation withpermeability of under100×10^-3μm², control target for suspended matter shall be that medianparticle size is under3μm and the concentration is under5mg/L; while for formation withpermeability of above200×10^-3μm², the same index shall be that median particle size isunder5μm and the concentration is under6mg/L.This thesis also studies the damage of various oil contents to permeability of formationcore under different temperatures through refinement of site crude oil and configuration ofcrude oil emulsion by adopting the method of core flowing test simulation. The results ofindoor core flowing test indicate that the effects of crude oil emulsion obtained greatlyinfluence the damage of core permeability; under the conditions of favorable emulsificationeffects, control target for oil content shall be20mg/L when the temperature of water injectionlayer is60℃, and30mg/L when the temperature is90℃.Besides, this thesis studies the influence of injection time on core permeability. Through long-time observation on water injection of many cores, the following results are discovered:the surface of core channel will be corroded by sewage as the injection time extends and corepermeability will increase gradually as the channel diameter expands. Within the beginningperiod if time, due to different bond strength of various cores, bond strength of core surfaceparticle will reduce and drop as a result of sewage corrosion, which then causes particlemigration and leads to such results: within short period of time, core permeability suddenlyrises after reduction, suddenly reduces after a period of time, then suddenly rises and finallybecomes stable; as the injection time extends continuously, core permeability will riseslowly.