THE CHARACTERISTIC OF ENERGY FIELD DURING THE KEY TECTONIC TRANSFORMATION PERIODS, TARIM BASIN

The Tarim Basin is an important superimposed basin in northwest China, and it experienced several periods of tectonic transformation during the geological history. The structure deformation, temperature-fluid pressure field and stress field during key tectonic transformation periods control hydrocarbon accumulation in the basin. Based on seismic, well data, outcrop and analytic data, we identified key tectonic transformation periods in the Tarim Basin. The characteristic of energy field in the study area is analyzed by numerical simulation. This work has important guiding implications for the oil and gas exploration in the Tarim Basin.

Based on the analysis of unconformity characteristic and fracture characteristic, The timing of four periods of key tectonic transformation is determined, including the Mid-Caledonian, th Early Hercynian, the Late Hercynian and Indosinian.

Numerical simulation has been considered as an effective method for analyzing the evolution of energy field. The results suggest that the geothermal gradient experienced a change of “decrease-increase-decrease” from the Mid-Caledonian to Indosinian. Abnormal pressure was mainly distributed in the Kuqa depression, the Manjiaer depression and the Tangguzibasi depression. The distribution and value of the excess fluid pressure increased gradually. The southern region of the Tarim Basin was in a compressional setting in the Mid-Caledonian and the Early Hercynian, followed by the Late Hercynian extension. In contrast, the northern region displays the opposite evolutionary trend from the Mid-Caledonian to the Late Hercynian. The Tarim Basin was dominated by compression stress field both in its northern and southern region in the Indosinian.