Reaserch Of Shooting Methods For Special Surface Condition In The West Area

In the west area of China, most oil-bearing area has a complex surface conditionor structure condition, most of its landform is loess, desert or mountainous region.The elevation changes very acute in the west area of China, and the surface conditionis very complex. With great lithological changes, complex deep structure, the westarea is hard to explore. Especially, when surface condition turn bad, earthquakestimulation and receiving became so hard. The SNR of seismic data is low, and itshard to form the imagery or affirm the structure, it brings much difficulty to dataprocessing. With the development of exploration, the main part of exploration projectmoves from area with good surface condition to area with bad surface condition. Soit’s an important problem to stimulate high-quality seismic signal.On the issue of seismic wave excitation, past research is more emphasis onmotivate factors research on the plain, and reserch of the western region specialsurface and deep complicated geological conditions in the western region is less.There isn’t an unique theory of excitation system in western China, this greatly hinderthe improvement of the western region of seismic exploration accuracy.In this paper, on the basis of the actual field, model of the loess tableland, desert,mountain surface interference and absorb the detailed surface is established, whichcontains the parameters include depth, density and speed of P wave and S wavevelocity, P wave and S wave’s quality factor. For the deep geological model, usingcomplicated structure such as the lens, normal fault, reverse fault, unconformitysurface, concave and convex interface, to make sure that the forward model can fullyshow the problem for the western region of seismic exploration. Using viscoelasticmedium wave forward modeling for records, we can clearly see the effect of westernspecial surface factors on the field seismic acquisition.In this paper, field seismic acquisition parameters selection is on the thoroughdiscussion, including the common characteristics and parameters of excitationlithology, seismic wave in viscoelastic medium, the transmission characteristics ofseismic wave attenuation characteristic in the process of transmission, and theapplication of virtual reflection principle. Large dose excitation is obviously does notproper for the loose surface of loess tableland, the desert. So in this paper introduces the principle of combination well inspire technology, and according to combination ofactual data are analyzed.Selection of the explosive factors is also very important in seismic waveexcitation, so in this paper, the blasting mechanism of explosive source are discussed,the details including, the formation of the shock wave of area near explosion, the soiland hard rock’s parameters of shock wave, explosion stress wave in the central regionand the far zone characteristics of elastic wave. And various parameters of columncharge. Then focused on the explosive when the choice facing the impedancematching and speed matching problem, aiming at the problem of speed matching,introduced delay blasting technology as one of the ideas to solve the problem.This article used a lot of field experimental data of the western region fieldseismic to discuss the acquisition parameters, then came up with the followingconclusions.1. Because of the complexity of the western special surface, it’s important tohave high quality surface factors investigation, and in the actual field collection, forthe choice of stimulation factors cannot treat as the same. It shall be held in point topoint design, so as to guarantee the quality of seismic acquisition.2.When choosing a excitation depth, excitation lithology of porosity and containwater should be considered. Try best to choose high P wave velocity and density,dense and stable strata as the excitation lithology.3.Properly use ghost wave can obviously increase the excitation energy, to ensurethat the seismic wavelet dominant frequency and bandwidth. In some parts of desertand loess tableland, there are ghost interfaces good to be used. For using ghostinterface, we should pay attention when using large dosage medicine column lengthchange, avoid the occurring of breakdown of the ghost reflection interface.4.In loess tableland and desert regions, because of the loose lithology andporosity, large dosage excitation will reduce the seismic wavelet dominant frequencyand bandwidth, but small dosage to excite seismic wavelet, its energy intensity isobviously insufficient. Using a multiple well combination with small dosage caneffectively solve the problem, but the combination of multiple well number has acritical value for improvement of seismic data quality improvement, should becombined with the specific experiments to determine the value.5.When selecting dynamite source, due to the strength of the seismic waveletenergy produced under the influence of explosive stability, many of the properties of explosives should be comprehensive considered,such as initiation energy, detonationvelocity of explosive, cartridge, cartridge shell quality diameter, charge density andradial clearance effect, powder particle size, etc.6.Selection of explosive type mainly consider two factors: wave impedancematch and speed match. It depends on the whole surface of the work area.