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Dipole cross sonic logging tool is a new generation of sonic logging tool. It ismainly used for measurements in soft formation, direct shear wave logging, parameter measurements of formation stress for drilling reference. This tool can acquire plenty of formation information in one trip, the survey method includes all present open hole sonic logging ways, and solve shear wave measurement in soft formation.

 It is composed of five sections, they are: electronic circuits, receiver sub, sonic isolator, transmitter sub and transmitter control circuit sub, shown in the following figure.

It is configured as lower transmitters and upper receivers, the toolsring sequence from top to bottom as: main electronic circuits, receiver sub, sonic isolator, transmitter sub and transmitter control circuit sub

1.  The monopole full wave logging:acquiring the speed of compress wave , shear wave, and stoneley wave to calculate the porosity of target formation.

2.  Identify gas reservoir :Δt of compress wave will change dramatically in the gas reservoir, while that of shear wave will change a little, so that the gas reservoir can be discovered by the ratio of compress wave speed and shear wave speed VP/VS.

3.   Investigation and evaluation of natural fracture.

4.   Indication of permeable bed.

5.   Determination of the formation anisotropy: the crossed dipole transmitter emits pressure bending wave into the formation ,received by crossed receivers ,If the formation is homogeneous, waveforms of X－X and Y－Y will arrive in receiver simultaneously, namely, they have the same transmitting time and phase. Otherwise, there should be some time and phase differences, so the formation anisotropism can be determined.. 

6.  Evaluation of rock mechanic properties: rock young’s module, bulk module and poisson ratio, which are the three important parameters of rock mechanic property.

The sonic system applies the structure of single transmitter and 8 receivers.

Total length：9.7 meter

Sonic source：

There are two kinds of sonic sources: monopole sonic source and two

dipole sonic sources that are cross arranged. The monopole transmitting

source is a piezoelectric ceramics ring transducer. X and Y dipole transmitting source are at the same depth point. They are piezoelectric ceramics three pieces pileup bender vibration transducer. Both X dipole and Y dipole sonic sources are composed of 2 transducers that are arranged at angle of 180°.

Receiving array：

For receivers: there are 8 receiving rings, each of which is composed of the 4 dipole receivers that are arranged at 90° in the circumferential direction. Both sonic source signals of monopole and dipole use all the 8 receiving rings as receivers. The distance between two adjacent receiving rings is 6 inches.

Monopole spacing：8 feet

Dipole spacing：9 feet

Transmitting source：Both monopole and dipole transmitting transducers are activated in way of power driving on the transmit excitation source. That enables the transmitting transducer work under forced vibrating mode to control the transmitting frequency. The main operation frequency of the monopole transmitting source is 8kHz. The dipole transmitting source has three operation frequencies: 1.2kHz,1.5kHz and 2.2kHz, they are selected by program to be applicable  soft formation (Δt>120us/ft), medium formation (100us/ft <Δt < 120us/ft) and hard formation(Δt< 120us/ft).

Receiving circuit：There are 32 independent receiver acquisition channels on circuits. Signals of each receiver channel are digitalized acquired. 

Working mode：A basic acquiring period is 1s. During an acquiring period, monopole , dipole X and dipole Y acquisitions will be executed once for each. The acquisition sequence is monopole, dipole X and dipole Y.

Max. temperature：150℃(IB) OR175℃（IC）

Max. pressure：  100MPa (IB) OR 140MPa（IC）

Borehole range：5”~12”

Max vertical resolution：6”

Max depth of investigation：1~3ft

Providing logs in real time：Monopole compress wave slowness, X dipole shear wave slowness and Y dipole shear wave slowness, quality monitor picture of these three logging curves in real time.

Providing logs after precise processing:speed of monopole compressive wave, attenuation analyze, Poisson ratio, rock mechanic properties, anisotropism of formation strains, fracturing height, stoneley wave field separation and permeability calculation more curves.