Experimental Research Of Oil And Water Seepage Rule Influenced By Low Frequency Pressure Pulse In Low Permeability Reservoirs

The low frequency pressure pulse technology，which make the wave energy producedby low frequency pressure pulse act on oil layer and make oil layer, as well as its fluid,produce physical and chemical changes, is to improve oil layer seepage condition, removereservoir jam，create the environment benefiting crude oil flow and achieve the aim ofincreasing the well production and the injecting volume of water. For more understanding ofthe theory that how the low frequency pressure pulse increasing production, in this article，thedetailed research is done, to discuss the effect of the low frequency pressure pulse to theoil-water seepage in low permeability reservoirs.Based at the research, we build theone-dimensional model to describe how the low frequency pressure pulse transmitting in thereservoirs, and discussed the character of the low frequency pressure pulse transmitting in thelow permeability reservoirs.Through the indoor experiment research and computation ofmathematical model, the following results are obtained:（1）The low frequency pressure pulse has a great effect on the permeability of single-phaseoil.As the increase of the pressure gradient, the permeability increases, up to25%highest. Adas the change of the pressure gradient, the increase changes, too. That is the lower the pressuregradient, the higher the increase. But when pressure gradient gradually increases, the pulseeffect significantly is weakened and the increase extent of oil phase permeability is decreasedgradually.（2）The oil permeability curve with the action of the low frequency pressure pulse has anon-Darcy flow character.And with the increase of the amplitude, the increase extent of oilphase permeability becomes higher.when the amplitude is4MPa, the permeability becomes3times higher than it is1MPa.Besides, as the decrease of the frequency of the low frequencypressure pulse, the oil permeability increases gradually. Take the chang4+5reservoir forexample, when the frequency is1/10Hz, the permeability curves are almost the same.Butwhen the frequency decreases to1/480Hz, the flow in the same pressure gradient increases as33.3%highest.（3）When the amplitude of the low frequency pressure pulse at about1MPa, the flow area of oil-water two phase becomes narrow, the equal permeability point is low, under thecondition of residual oil saturation the water phase relative permeability is big, compared withconventional oil displacement, the permeability curve is almost the same.But when theamplitude increases to4MPa,the pulse function greatly broadens the channel of oil and waterflow and improves the flow ability of the oil and water. Oil-water two-phase of the core withthe pulse function increases apparently, the range is up to24.33%, the increase range of theequal permeability point and the water phase relative permeability of residual oil saturation are80%and74.7%.（4）When the low frequency pressure pulse acts on different frequency, with the decreaseof the frequency, the flow area of oil-water two phase becomes broader, the equal permeabilitypoint becomes higher, the water phase relative permeability of residual oil saturation becomehigher too.When the frequency is1/60Hz, the relative permeability of the equal permeabilityis0.147,the permeability of water is0.359.whe the frequency becomes to1/120Hz, thenumbers become to0.215and0.592.（5）When the low frequency pressure pulse spreads in oil layer, with the decline of oilphase viscosity, the permeability of reservoir increase, the frequency of the pulse decreases,the attenuation speed of the low frequency pressure pulse amplitude becomes slower, theeffective propagation distance becomes further.