Tectonic Controlled Rapid and High Efficient Hydrocarbon Charging in the Central Daqing Anticline (Cda) of the Songliao Basin: Geochronologic Evidences from Fluid Inclusion Analysis and Authigenic Illite Dating
The Songliao Basin is one of the biggest lacustrine basins in the world with a total area of 2.6×105 km2. The exploration and development of the Daqing Oil Field in the Cetral Daqing Anticline (CDA) has played a key role both in the development of the petroleum industry in China and in the advancement of none-marine petroleum geologic theory. Systematical fluid inclusion analysis (FIA) and Authigenic Illite Dating (AID) indicate a high efficient and instant hydrocarbon charging controlled by a rapid folding and uplifting of the BDA.
There exist two periods of fluid movements in the CDA. Fluid inclusions of the first period are distributed isolatedly in the quartz and trapped in a homogenous state with a low concentration of hydrocarbon fluid inclusions (GOI<5%). Fluid inclusions of the second period are trapped in an inhomogeneous state indicated by linear distribution along the fissures or cracks of the autogenetic mineral and higher homogenous temperature than the maximum burial temperature. Hydrocarbon charging happened mainly in the second period indicated by a high GOI concentration (GOI >15%) .
The hydrocarbon accumulation process in the CDA is a typical anticline model indicated by the age model. Both positive and negative relationships between the age of authigenic Illite dating and the sampling depth have been found. Positive relationship indicates that hydrocarbon accumulated earlier in the lower reservoir than that in the upper, while negative relationship indicates vise versa. Wells with positive relationship are distributed mainly in the axis of CDA, while those with negative relationship distributed in the flank with the height lower than -900 m.
Age space distribution indicates a high efficient and instant hydrocarbon charging controlled by tectonic folding. All the strata of the CDA under the main seal of the Nenjiang Formation with height>-900 m has been charged in the period of 59~69 Ma. The total oil and gas produced in this range is about 7×109 t, which means that the amount of hydrocarbon charging is about 2 t/day at least. The results suggest an episodic hydrocarbon migration and accumulation controlled or triggered by the tectonic movement in contrary to the common thought of overpressure.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009