پیشنهاد الگوریتمی برای مدل‌سازی و تفسیر داده‌‌های سایزموالکتریک

نوع مقاله: مقاله تحقیقی‌ (پژوهشی‌)

نویسندگان

دانشگاه آزاد اسلامی، تالش، ایران

چکیده

به طور کلی روش سایزموالکتریک، روشی اکتشافی براساس امواج لرزه‌ای و الکترومغناطیسی است. امواج لرزه‌‌ای ایجاد شده با یک چشمه لرزهای در مرز جدایی دو محیط، حرکت نسبی سیال–جامد را به‌وجود می‌‌آورند که در اثر تقابل خواص کشسانی محیط با سیال اشباع‌‌کننده ایجاد می‌‌شود. هدف از این تحقیق، بررسی تاثیر میدان الکتریکی جریان DC روی انتشار امواج ارتعاشی به روش حوزه زمانی شبه‌‌طیفی (pseudo spectral time domain) است که در اصطلاح کلی‌‌تر، تاثیر اتصال سایزموالکتریک نامیده می‌‌شود. در این تحقیق از معادلات پروالاستودینامیک برای امواج ارتعاشی و معادلات ماکسول برای امواج الکترومغناطیسی استفاده شده و میزان تاثیر اتصال سایزموالکتریک با چگالی بار الکتریکی، قابلیت رسانایی الکتریکی، تابع قابلیت نفوذ دی‌‌الکتریک، گران‌رَوی سیال و پتانسیل زتا تعیین شد . تغییر میدان الکتریکی با جریان الکتریکی DC اعمال شده با نتایج آزمایش فیزیکی در محیط مدلسازی شده مقایسه شد و  نتایج روشن ساخت که میدان الکتریکی DC به طور قابل توجهی روی انتشار انرژی کشسانی از راه اتصال سایزموالکتریک در محدوده وسیعی از پهنای بسامد ارتعاشی تاثیر می‌‌گذارد . همچنین  به کمک مولفه افقی میدان الکتریکی موج الکترومغناطیسی، مرز لایه‌‌های زیر سطح زمین مشخص شد.

کلیدواژه‌ها


عنوان مقاله [English]

An algorithm for the modeling and interpretation of Seismoelectric data

نویسندگان [English]

  • Mirsattar Meshinchi Asl
  • Hooman Latifi
چکیده [English]

Seismoelectric modeling is a prospecting method, based on seismic electromagnetism in which seismic sources are used to generate this phenomenon. When seismic waves are released within a fluid-saturated sedimentary material, a small amount of fluid-solid relative motion is induced. The seismic force causes this effect through a combination of relative gradient acceleration fluid and the pressure of seed waves. Most of the surface grain, in contact with a liquid electrolytes, are chemically bound to the surface load. The thin layer of charged fluid around each grain is balanced with a scattered distribution of mobile ions with opposite charges. The scattered ions in this layer are free to move through the fluid so that seismic waves create an electrical current flow. This induced seismic current flow acts as a current source in Maxwell's equations, which is the base of electromagnetic wave coupling with a seismic wave. The peaks and troughs that accumulate are P-type waves. The electric field is produced inside the wave (seismic), which is vertical on the wave sinciput. This flow creates convection. In a homogeneous substance, the current flow is equal to convection so that the overall flow is zero; no magnetic or electromagnetic fields are created independently., Hence, the electric field that exists within the wave moves as a part of the reaction without spreading outside the wave. Therefore, a simple pair of electrodes can act as a geophone to measure the electric field inside the P-wave when it passes throughthem. The S shear wave does not separate charges in a homogeneous substance without divergence, so they cause no fluid repletion. The relative motion of fluid to solid is due to seed accelerations. The induced current flow creates magnetic fields that, in turn, produce a small electric field. Thus, for S waves in a porous and homogeneous environment, a magnetic field is produced that moves as a part of the material reaction. Effluent but electromagnetic waves are not produced independently. Supposedly, a magnetic detector (which is insusceptible to mechanical vibration) can serve as a selector geophone on shear wave action and measure the magnetic field N-S wave when the magnet passes the gauge. The effect of a direct current (DC) electric field on the propagation of seismic waves is modeled in this study by means of the pseudospectral time domain (PSTD) method, based on a set of governing equations for poroelastic media. This study focuses on the more general concept of the siesmoelecric coupling effect and the application of poroelastodynamics and Maxwell's equation to seismic and electromagnetic waves. In this project, the magnitude effects of seismoelectric coupling are found to be characterized by charge density, electric conductivity, dielectric permittivity, fluid viscosity and zeta potential. The simulated poroelastic wave propagation and electric field vary with an existing background. A physical experiment was carried out in an oilfield using a DC electric field and the results were compared with those of the simluation. Estimations for solutions of differential equations are based on the function (or a number of separate estimates for this function) defined by a certain relationship between its various derivatives on a given place or time range along the boundary conditions of this area. Overall, this is a serious problem and only a formula for this solution was analyzed. An alternate method with finite derivatives was used to replace the differential equation. The results show that the seismoelectric coupling in a wide range of the seismic frequency bands generated through a DC electric field can significantly affect the propagation of elastic energy.
 

کلیدواژه‌ها [English]

  • electric field
  • pseudospectral time domain
  • poroelastic media
  • seismoelecric coupling
  • pore pressure