| In recent years, exploration targets are gradually turning to the more difficult deep formations of the lower third Member, the fourth Member of Shahejie Formation and Kongdian Formation from the upper middle third Member of Shehejie Formation in Dongying depression. Deep hydrocarbon explorating fruits has suggested that there is high exploration potential in the deep formation of Jiyang depression. However, compared with the shallow formation, deep reservoir quality is poorer, and the temperature and pressure are higher, which show there are great difference for hydrocarbon accumulation condition between them. The model established in the shallow formation can not be directly applied to the deep petroleum exploration. Hydrocarbon charging mechanism and forming model in deep formations become the problem to be solved. In this research, fluid inclusion analyses including fluorescence colors, homogenization temperature and salinity measurements have been exerted on 144 samples from 29 wells in north belt of Dongying depression.This paper studied the hydrocarbon charging mechanism and forming model by researching the timing of hydrocarbon accumulation, the origin of natural gas, the paleo-temperature, paleo-pressure and the paleo-fluid potential. The main conclusions are as follows:1. There were two phases of hydrocarbon charging in this three area, the first phase is between 38.4-24.7Ma, which was occurred from the middle of the third member of Shahejie Formation to the end of Dongying Formation and the second phase is between 12.5～0Ma, which was occurred from the middle of Guantao Formation to the present in Lijin area. The main period of hydrocarbon charging was in the second period in Lijin area. The first phase is between 39-31.9Ma, which was occurred from the middle of the third Member of Shahejie Formation to Dongying Formation and the second phase is from 13.0～0 Ma, which was occurred from the middle of Guantao Formation to the present in Shengtuo area. The first phase is between 41～36Ma, which was occurred from the middle of the third Member of Shahejie Formation to the end of the second Member of Shahejie Formation and the second phase is from 13.4～0 Ma, which was occurred from the middle of Guantao Formation to the present in Minfeng area. There are a large amount of hydrocarbon charging in the first and the second period in Shengtuo and Minfeng area, but the second period is the main charging period.2. The evolution of paleo-pressure experienced two phases, corresponding to the two hydrocarbon accumulation. The first phase of 38.4-24.7Ma is characterized of normal- abnormal overpressure system, and the second phase of 12.5～0Ma began to appear strong abnormal overpressure in Lijin area; The first phase of 39-31.9Ma is characterized of normal- abnormal overpressure system, and the second phase of 13～0Ma began to appear medium-strong abnormal overpressure in Shengtuo area. The first phase of 41-36Ma is characterized of normal- abnormal overpressure system, and the second phase of 13.4～.0Ma began to appear abnormal overpressure-normal pressure in Minfeng area. The pressure coefficient decreased through time evolution.3. The accuracy of the homogenization temperature of fluid inclusions and PVT modeling have been proved to be reliable. The homogenization temperature of the last phase of hydrocarbon charging is about 41℃higher than present-day formation temperature in Lijin area, about 31℃higher in Shengtuo area and about 45℃higher in Minfeng area, which reflects Dongying depression experienced a automatic cooling geological process in the thermal subsidence phase.4. Crude oil densities in hydrocarbon inclusions decreased with burial depth, this is probably caused by hydrocarbon muti-stages migration and charging from deep to shallower formations, and may also related to nature oil cracking and gas inclusion. The deep reservoir quality is not better than that of the shallower formations because of the higher pressure and higher temperature, and critical conditions of oil and gas charging also become smaller in the deep buried formations. The two phases of paleo-fluid potential are different. In the first phase, higher potential area is distributed around Tuo710 well of Shengtuo area, the second higher potential area is Minfeng depression. In the second phase, Linjin and Minfeng area are two high potential areas, the surrounding area with lower potential is the favorable hydrocarbon accumulation belt.5. Based on the above research, the hydrocarbon reservoir model of the three areas are built: medium oil in the centre of Lijin area migrate upward along fractures formed by overpressure discgarging in the first period. The second period is mainly charging for crack gas, and it is considered that kerogen-cracking gas charging is the primary charging in Lijin area. In the first period, it is mostly charging with lower mature oil in Shengtuo area, early generated oil and gas migrate upward along the fault, unconformity surface and the connected sand bodies, and oil reservoir formed. It is mainly charging for highly mature oil in the second period, the late generated oil and gas migrate upward along the connected sand body, the fractures formed by overpressure. It is mainly charged with normal mature oil in the first period of Minfeng area, oil and gas did not reach in the structural high location due to low fluid potential, there is a large amount of crude oil charging in the second period. It is charged with condensate gas after the normal crude oil charging, temperature is high in the period of condensate gas filling, the crude oil began to crack, the cracking gas migrate upward along microfractures.
|
PDF Full Text Request