Abstract:

The petroleum exploration prospective of deep strata in rift depression is always concerned by lots of geologists. Xinglonggong area, closely adjacent to Baxian depression which is the petroleum generation depression, has many advantageous hydrocarbon accumulation conditions. In this area, some industrial petroleum traps were searched in Dongying Formation and 1^st Member of Shahejie Formation. The petroleum exploration degree of this area was much lower than those of other places in3^rd Member of Shahejie Formation, which was the deep strata in the Baxian depression, although a few exploration wells confirmed that there were some favorable elements to hydrocarbon's accumulation, especially, to the stratigraphic reservoirs. According to hydrocarbon accumulation theory of petroleum geology, the favorable conditions of stratigraphic hydrocarbon accumulation and trap models discussed in this paper are as follows: Firstly, the hydrocarbon sources are sufficient because the traps of the 3^rd  Member of Shahejie Formation are close to source rocks which are shales from the 4^th, 3^rd , and 1^st members of Shahejie Formation; Secondly, the reservoir conditions are very good owing to the sandbodies of large scale delta front and some turbidity deposition; Thirdly, oil accumulation of stratigraphic reservoir benefits  from the slope breaks and synsedimentary structures; Finally, the gypsum, gypsum shales, shaly gypsum, halites and shales can act as caprocks. According to the structure area dividing, three areamodels of stratigraphic petroleum trap are summarized: abrupt slope, gentle slope and depression models. In abrupt slope area, structurestratigraphytrap and small scale delta front sandbodies developed. In gentle slope area, hydrocarbon is prone to accumulate in large scale delta front, overlapping strata and some sandbodies adjacent to unconformityHowever, in the depression area, pinched out sandbodies are typical, i.e., below the break areas of abrupt slope, fan delta front reservoirs and turbidity sandbodies are favorable petroleum traps, and under those areas of gentle slope, delta front reservoirs, turbidity sandbodies and sheet sand bars are the places for  hydrocarbon accumulation in the low system tract. According to the studies of petroleum accumulation elements and trap models, those areas below the break point of Wenan gentle slope in the east part of Xinglonggong area are considered to be the most profitable place for hydrocarbon exploration.

Key words:  Xinglonggong area, Baxian depression, 3^rd Member of Shahejie Formation, stratigraphic oil/gas reservoir, trap model of petroleum accumulation