Study On Residual Resources And Exploration Directions Of Oil And Gas In Shallow To Middle Formations, North Of Songliao Basin

Statistical data of hydrogen indexes and thermal modelling of the source rocks with different abundant organic matter indicate that hydrogen indexes both of the immature source and the mature source rocks by recovery are all 750mg/gTOC, while the lowest value of residual hydrocarbon is 100mg/gTOC. The standards of the effective source rocks can be established by the values of hydrogen index（650～100mg/gTOC）, hydrocarbon index（40～100 mg/gTOC） and RO（0.75～1.2%）, and the limit RO value（0.5%） before does not fit the new standards.Dynamic modelling of the source rocks of different abundant organic matter and type reveal that the source rocks with different types have the same dynamic parameters with a narrow activity energy distribution which takes a short time from the beginning to the highest generation stage, and the low mature are needed to the high organic matter source rocks. The expelling limit is 15% of the hydrocarbons. The effective source rocks in different formations with different organic abundance mainly locate in the central areas of Qijia-gulong and Sanzhao depressions. The expelling amount of qn1 formation takes the highest values, and the qn2+3 formation takes the second largest values. Meanwhile, the effective source rock distribution areas of n1 and n2 are very small which can only be observed in some regions in Qijia-Gulong depression. According to this consideration, the oil resources can be calculated with the values of 126～152×10⁸t which have increased 31.7～57.7×10⁸t and 23.6～25.3×10⁸t respectively compared with the second and the third national resource eveluations of oil and gas.Based on the distributions of effective source rocks, correlations between oil （gas） and source rocks, and coexistence of oil and gas, three complex petroleum systems （upper, middle and low）, K₂qn₁+K₁（sha+ych）—K₁q（3+4）（!）, K₂q_n1+2+3+K₂n₁—K₂（n1+y（2+3）+ y1+q_n（2+3））（!） and K₂q_n（1+2+3）+K₂n（1+2）—K₂n（3+4）（!）, have been recognized which can be subdivided into seven simple petroleum systems. The controlling pool accumulation factors in the low complex petroleum system are the effective source rocks, the physical properties of the reservoirs and the T2 faults; The controlling pool accumulation factors in the middle complex petroleum system are the effective source rocks, large structures, the front facies of deltas and the migration paths; The distributions of the effective source rocks in the upper complex petroleum system are very limited, the structures and the faults take important rolls to the pool accumulations.The results of oil and gas resource evaluations in different time are not the same. We should takes 86.3～113.3×10⁸t as the values of the oil resources which the expectation value is 94.3×10⁸t. The total amount of oil resources predicted by the pool discovery process model of Putaohua, Fuyang, Gaotaizi and Saertu oil formations is 943867×10⁴t; meanwhile, the total residual oil resources is 362530×10⁴t.Weibull model et al. have been utilized on the predictions of the middle to shallow oil formation’s reserve increases. By these predictions, during the next 10 years, the oil reserve increases may be within 4000～7000×10⁴t each year. Five regions, such as Daqing structure, Sanzhao depression, as well as Qijia depression, ect. may have 5×10⁸t proven reserve ability. 300～500×10⁸m³ shallow natural gas will be discovered.