Study on the Highest Rock Paleotemperature with Thermo-acoustic Emission

Thermal history reconstruction of the sedimentary basin is significant to hydrocarbon exploration as temperature affects hydrocarbon generation. Thermal history is mainly reconstructed with the paleothermal indicators that are used to study temperature by kinetic properties. This study may provide an available method, rock thermo-acoustic emission technique, to directly measure the highest temperature rock experienced.

Repetitive thermal loads may induce a thermal Kaiser effect similar to the case of the mechanical Kaiser effect, which is the base of rock temperature measurement with acoustic emission. If rock is heated, the number of acoustic emission signals will increase dramatically at some temperature which is considered as the highest it experienced.

Artificial heated samples are used to test the thermal Kaiser effect in sedimentary rocks and discuss the accuracy of the results. The artificial sandstone samples and limestone samples are first heated to 200 and 400 centigrade degree respectively, then cooled down. In the acoustic emission experiment, the sandstone samples are heated to 240 centigrade degree at the same heating rate and the limestone samples are heated to 430 centigrade degree at different rates. Then temperatures of sandstone samples and mudstone samples in different depth of the Tarim Basin are measured with thermo-acoustic emission. At last a sample in Sichuan Basin is applied to study the influence of time. Acoustic emission signals are record while each sample is heated.

After filtering out signals without any energy, the highest temperature rock experienced is determined when many signals appear suddenly. Signals vary obviously with the increase of temperature. The temperatures of artificial sandstone samples range from 190 to 198 centigrade degree with an average of 194 centigrade degree. The temperatures of artificial limestone sample are from 369 to 409 centigrade degree with an average of 388 centigrade degree. The measured value of each sample of the Tarim Basin is close to the highest temperature calculated based on previous researches. The sample in the Sichuan Basin shows that the influences of time can be accepted.

The results illustrate good Kaiser effect for sedimentary rocks and the heat rate has no influence on measured values. Comparisons between the measure and actual values suggest the thermo-acoustic emission can be applied in rock paleotemperature measurement.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California