Study On Tectonic-thermal Evolution And Its Relation With Petroleum-gas In Kongquehe Area In Northeastern Tarim Basin

Kongquehe region is a typical superimposed area in northeast Tarim basin, which superimposed and reconstructed by different prototype tectonic movement. The evolution of different sets of source rocks is controlled by basin buried history and thermal evolution history. The study of basin thermal evolution and source rock thermal evolution have an important role in the basin thermal evolution characteristic in foreland area of the edge of northeast Tarim basin and affects hydrocarbon generation.In combination with regional tectonic background and geological features of Kongquehe slope, the idea of recovering tectonic-thermal evolution history based on superimposed basin is introduced. Starting from an analysis of denudation and buried history, tectonic-thermal evolution history was recovered and reconstructed by several palaeotemperature scale studies. This paper makes a further study on Cambrian-Lower Ordovician thermal history, hydrocarbon generation and formation stages of bearing oil-gas reservoir and sums up the major control factors, establishes petroleum accumulation patterns and makes clear the further exploration tendency.In the first time, confined to the regional tectonic background, Kuruktag uplift stages and its effects on the Kongquehe slope are researched by the Zircon and Apatite fission track thermochronology. The study shows that there exist two stages of uplift processes which are late Caledonian started Hercynian and late Crataceous periods respectively. And each stage plays a different role in the Kongquehe slope. The first uplift makes the long term burial stage in Kongquehe area stop and enter into a process of tectonic uplift-erosion stage, and results in the thermal evolution degree of Cambrian-Lower Ordovician source rocks ceased. Late Crataceous uplift makes the Mesozoic trap complete. Kongquehe fault forms thrust and nappe tectonic style, and thermal evolution of Jurassic source rocks increases.According to the study of stress field changes and tectonic burial history and faults formation stages, the original basin can be divided into four styles. Each one has its special evolution character. On the basis of calculations of erosion thickness, study area can be classified into 4 burial styles: there are early-uplifts and late shallow bury belt in paleaohigh, early deep bury and late adjustmengt in slope belt, successive burial process in depression and one time uplift late deep burial in Yingjisu depression.With several palaeotemperature scale synthetical studies, the thermal evolution history in different tectonic units is recovered using EASY%Ro single-well modeling. Results implies that paleaothermal gradient evolution tendency is identity with regional paleaothermal gradient evolution regulations. The value of Palaeozoic thermal gradient is higher than Mesozoic and the value of Cenozoic is the lowest, the evolution history takes on a characteristic of slowly decline changes. Controlled by the burial and thermal history, thermal evolution of Cambrian-Lower Ordovician source rocks has a characteristic of early generation, diversity mature in different tectonic units. The largest thermal mature degree in paloeohigh area is formed in late- Ordovician, generation liquid hydrocarbon and that formed in late Devonian to early Silurian in Kongquehe slope and yingjisu depression. Deep burial and thermal metamorphism make the thermal mature degree in Cambrian-Lower Ordovician source rock and palaeo-reservoir further increase. Yingjisu depress has the ability of secondary hydrocarbon generation. The thermal evolution history in Caohu depression specialized in successive matured style still has the ability to hydrocarbon generation. Early Devonian, the source rock in Manjiaer depression gets to the beyond-mature degree, and is during the condition of invalid hydrocarbon generation area.On the basis of single-well model, combing the study of tectonic-burial history, conclusion can be drawn that there exist 3 kinds of hydrocarbon generation type: (1) early single generation type in palaeohigh area; (2) successive generation type in Caohu area; (3) single generation and over-matured evolution type in slope area.After the study of typical reservoir analysis, with the application of Oraganic inclusions, clay mineral terminology and laser Raman microprobe methods, the formation stages of Silurian, Jurassic bearing oil-gas reservoir of Qk1 were studied detailed in the first time. Characteristic in the Kongquehe is early reservoir forming, multi-stages destroying and adjusting, late second-reservoir forming. Results show that the formation stages of Silurian wed-gas reservoir is in Hercynian period. It implies that Cambrian-Ordovician palaeo-reservoir is destroyed hardly in Hercynian period, in addition of absence oil-gas coming from the below, the migration of Jurassic is largely original from the effusion and second migration of residual Silurian wet-gas. The new cognition about formation stages of oil and gas is important for the next exploration of Kongquehe area.Based on forecasting and evaluating of the key object, with the guidance of hydrocarbon generation and hydrocarbon charging period, this paper points out Silurian, Jurassic reservoir of anticline structural zones in Longkou tectonic belts and Silurian reservoir of anticline structural in Weima-Kaiping are advantageous exploration zones.