SU890295A1

SU890295A1 - Method of excitation of elastic signal in water

Info

Publication number: SU890295A1
Application number: SU802909614A
Authority: SU
Inventors: Алексей Маркович Грибанов; Юрий Александрович Москаленко
Original assignee: Южное производственное объединение по морским геологоразведочным работам "Южморгеология"
Priority date: 1980-04-10
Filing date: 1980-04-10
Publication date: 1981-12-15

Description

II

Изобретение относитс к области возбуждени импульса давлени в водной толще и может быть использовано дл проведени сейсмических исследований на море.The invention relates to the field of pressure pulse excitation in the water column and can be used for seismic surveys at sea.

Известен способ возбуждени упру-гого сигнала в воде, при котором генерируетс короткий сигнал, заключающийс в том, что взрыв взрывчатого вещества производ т в жесткой перфорированной сфере определенного радиусар.A known method of exciting an elastic signal in water, in which a short signal is generated, consisting in that an explosive is produced in a rigid perforated sphere with a certain radius screen.

Недостатком этого способа вл етс понижение излучаемой акустической мощности, сложность его реализации.The disadvantage of this method is to reduce the radiated acoustic power, the complexity of its implementation.

Известен также способ сосредоточени излучаемой энергии в узкой полосе частот путем погружени источника на глубину, равную четверти преобладающей длины волны регистрируемых колебаний 2J.There is also a known method of concentrating the radiated energy in a narrow frequency band by immersing the source to a depth equal to a quarter of the prevailing wavelength of the detected oscillations 2J.

Однако данный способ не позвол ет исключить пульсацию газового пузыр и сократить длительность излучаемого сигнала.However, this method does not eliminate the pulsation of the gas bubble and reduce the duration of the emitted signal.

Наиболее близким по технической сущности к предлагаемому вл етс способ возбуждени упругого сигнала в воде, включающий расширение сжатого газа в воде, дополнительное вдувание определенной порции воздуха в момент максимального расширени газового пузыр , при котором излу10 чаетс короткий сигналГз.The closest in technical essence to the present invention is a method of exciting an elastic signal in water, including expansion of a compressed gas in water, additional injection of a certain portion of air at the moment of maximum expansion of a gas bubble at which a short signal is emitted.

Недостаток известного способа заключаетс в том, что дл его реализации требуетс конструктивно сложное устройство, способ имеет низ15 кий КПД.The disadvantage of the known method lies in the fact that its implementation requires a structurally complex device, the method has low efficiency.

Целью изобретени вл етс сокращение длительности излучаемого сигнала , по сравнению с общей продолжительностью пульсации газового пузы20 р ,-без уменьшени КПД источника.The aim of the invention is to reduce the duration of the emitted signal, compared with the total duration of the gas bubble pulsation of 20 p, without decreasing the efficiency of the source.

Claims

The goal is achieved by the fact that, according to the method of exciting an elastic signal in water, including the source source at a predetermined depth and expansion of the compressed gas, the energy of the compressed gas is selected so that the period of the first pulsation of the gas flow becomes equal to the doubled immersion depth source. The method is carried out as follows. When the seismic vessel moves along the profile, the depth of the source is determined depending on the required frequency of the emitted signal. According to the known immersion depth and velocity of the elastic signal in water, the travel time is determined by a time signal equal to twice the depth of the source. Then, depending on the type of source, the energy of the compressed gas is selected (by changing the initial pressure to volume) such that the period of the first pulsation is equal to the travel time by a signal of twice the source’s immersion depth. When implementing the proposed method, the wave reflected from the surface of the elastic wave approaches the bubble in opposite phase and suppresses the subsequent 4 pulsations. Thus, a short signal is emitted. The method of exciting an elastic signal in water, including immersing a source to a predetermined depth and expanding compressed gas, characterized in that, in order to reduce the duration of the emitted signal while maintaining acoustic efficiency, the energy of the compressed gas is chosen so that the period of the first pulsation of the gas bubble becomes the travel time by the signal of the doubled immersion depth of the source. Sources of information taken into account in the examination 1.KnudseriW. S. El Imlnation of secondary pttessure pdlses in offshore exploration. Jeophysics, 1961, No. 4, V. 24.

2. Balashkand M. I, Lovl S. A. Sources of excitation of elastic waves in seismic exploration in water areas. M., Nedra. 1977, p. 31.

3. US patent number 3601216, cl. 181-5, pub. 1971 (prototype).