Research On Seismic Monitoring Of Heavy-Oil Thermal Recovery In Shengli Oil-Field

There are a vast amount of heavy-oil in Shengli oil-field , injecting overheated-steam were used to enhance heavy-oil recovery at present . Monitoring thermal pilot by seismic methods had benefited oil-field development a great deal.Different kinds of heavy oil cores from Shengli oil-field were respectively tested to determine the relations between seismic wave velocities and temperature or pressure etc. The researches lead to the conclusion:(1) When ambient temperature is 25℃,and country Pressure is 10Mpa, There is a parabolic relation between heavy oil content in sand core and P-wave velocity Vp Vp in 100% heavy-oil saturated sand core monotonously decreases with temperature rise, which shows an approximate linear relation. When the pressure is 30 Mpa, the relation between Vp and temperature is characterized by a hyperbolic curve.(2) The influence of temperature upon the normalized initialamplitude of P-wave in heavy-oil sand core can be seen at mid and low temperature.The normalized shear modulus G/Gmax of sand core declines linearly with the increase of temperature .(3) When temperature is constant, VP shows an approximate linear increase with country pressure ; and country pressure effect is more obvious at low temperatures than at high temperatures .The thief-zone model of heavy oil thermal recovery and the associated geophysical parameter model by computers proved this solution :(1) There is a closely relation between heated heavy-oil seismic reflection and the amount of steam rejected and velocities decline .(2) The amplitude obviously increased with the amount of steam injected rised.(3) The main frequency decreased after saturated heavy-oil were heated.Monitoring of throughput-well in high resolution seismic measures conducted this results : (1)The amplitude of seismic event were strengthened afterpost-injection .(2) Pushdown of seismic event were evident on heated zone .(3) On energy spectrum map P-wave declined 350m/s afterheavy-oil heated . (4) The length of thermal fronts was 180m around thethroughput-well on the section difference figure . (5)There were 3.4ms time-delay in vertically and 180m expandedrange in latterly on amplifier amplitude graph processed byinteractive station . (6) The seismic reflection near survery well were weak , due to theinformation were the reflection of unsaturated-sand not thus ofsaturated heavy-oil.High resolution acquisition, processing and interpretation were applied to steam-drive well come to this conclusion .(1) Thermal fronts domain were 230m after 12 months , among them were 110m in the northeast , and in the southwest were the residual.(2) After 18 months , the length of thermal pilot were 310m in the northeast and in the southwest were 240m .(3) From steam drive well to both directions , the radiation zone of interval velocity decline were 635m , it's 275m in the northeast, and the remainder were in the southwest . Interval velocity dropped 17 percent.(4) The variation zones of frequency were about 590m . It's 370m in the northeast, and the remainder were in the southwest . Thedropped ranges of principal frequency were 6Hz .(5) The more strength of amplitude in pre-injection , the more strength in post-injection , rate of increase were 20 percent ; conversely ,the more weak of amplitude in pre-injection , the more weak in post-injection ; rate of reduce were 25 percent.(6) Compare the seismic information with temperature, pressure, degree of saturation of heavy-oik degree of saturation of steam and the situation of production well, we could see the techniques of seismic monitoring were extremely reliabity , the thermal fronts were 550m ± 40m about.The success of heavy-oil thermal recovery by seismic methods open a new way for geophysical techniques which used to oil development . It's very important for enhanced oil recovery and declined consumption energy .