Experimental Study Of Seismoelectric Logging

Some relative motion between solid and fluid phase will appear, which furtherleads to electric field accompanying elastic wave, when elastic wave travels throughsaturated porous rock due to the net ions in the saturated rock pores with water. Thisparticular property, which is related to elastic wave’s seismokinetic effect, especiallyexists in permeable pore media, is also called seimoelectric effect. The article is mainlyto make a discussion about seismokinetic logging’s feasibility with the method ofrecording acoustic as well as electric field after the acoustic wave’s emission. Aftertheoretical analysis of the technique, it is placed more emphases on the construction ofthe measurement and acquisition experimental system to receive acoustic and electricsignals.With the previous scholar’s jobs’ foundation in the first section, based on theseimokinetic coupling equations and boundary conditions in the borehole, it is derivedand simulated acoustic and accompanied electric field in a porous borehole, whichmakes it easier to recognize the characteristics of seismoelectric logging’s signals. Ithas been demonstrated that it can be measured compressional wave, shear wave,stoneley wave and their accompanied electric signals in porous borehole models.Compared with acoustic signal, electric signal’s wave shape and arrival time are almostthe same, but extremely lower in amplitude.Acoustic logging experiments and seismoelectric logging experiments are carriedout with the above system in the second section. However, it is found that electricsignal tends to be so tiny and weak in amplitude that it can even reach microvolt andnanovolt. Therefore shielding boxes, sliver papers, high density cables, commonground connection and double channel filter, et al are applied to the experimental system to get rid of the inferences of noises. Additionally, it is obvious that the abovemeasures are effective and clear electric field waves are collected in the experiment. Totest the experimental system’s reliability and effectivity, a comparison betweenreceived electric signals on the surface of rock model by the means of moving sourcewith the same distance and the direct acoustic wave recorded in the same wave ismade.Acoustic longing and seismoelectric logging experiments are carried out in luciteand two different kinds of sandstone model to record acoustic and electric field in thethird part. In sandstone, acoustic field waves as well as electric field waves, both ofwhich are of the same tendency in the shape and receive compressional wave, shearwave and stoneley wave, has been recorded. Meanwhile, every section in the full wavein acoustic and electric field has proven to be of the same velocity and relativeamplitude. However, it can be only obtained acoustic field but no electric field in aLucite borehole model, which confirms the theory that seismoelectric effect can onlyhappen in the saturated porous media and the accompanied electric field wave accordsthe basic principle of acoustic field wave in the borehole. It can be inferred that porousmedia’s properties, such as porosity, tortuosity and permeability, have a drasticinfluence on seismoelectric effect by the comparison between the experiment results oftwo sandstone borehole models. What’s more, it can further present seismoelectriclogging’s invaluable prosperity in logging engineer project domain.