准噶尔盆地西北缘深层油气成藏底限及其判别

随着含油气盆地中浅层勘探开发程度的不断提高,深层成为未来油气勘探的重要领域.近年来,准噶尔盆地西北缘在深层勘探取得了重要突破,但随着研究区勘探深度的不断加大,储层物性不断变差,油气成藏底限受到越来越多的关注.以准噶尔盆地西北缘地质、测井、试油、分析化验等资料为基础,综合运用束缚水饱和度法、最小流动孔喉半径法和储层内外势差法,对准噶尔盆地西北缘油气成藏底限进行了研究,并用实际钻探结果进行验证.结果表明:准噶尔盆地西北缘油气成藏底限对应的孔隙度介于1.9 % ~2.2 %,深度底限介于6 500~7 000 m,孔喉半径约为0.036 μm;油气成藏底限之下,储层自由流体空间消失,储层失去渗流能力,储层内外有效势差为0,导致成藏作用结束,无油气勘探潜力.

Bottom boundary of deep hydrocarbon accumulation in northwestern margin of Junggar Basin and its identification

With gradually enhanced explorations in middle-shallow layers of petroliferous basin, deep layers become an important area for future petroleum exploration. In recent years, great breakthroughs have been made in deep exploration in the northwestern margin of Junggar Basin. With the increasing depth of exploration in the study area, the physical properties of reservoir gradually become poor, and the bottom boundary of hydrocarbon accumulation has attracted increasingly more attention. Based on geology, well logging, oil testing, analysis and assay data, a study on the bottom boundary of hydrocarbon accumulation in the northwestern margin of Junggar Basin is conducted using the method of irreducible water saturation, minimum flow pore throat radius and potential difference inside and outside reservoir, which is verified by the actual exploration results. The research results show that the bottom boundary of hydrocarbon accumulation in the northwestern margin of Junggar Basin has the porosity of 1.9 %-2.2 %, depth of 6 500-7 000 m, and flow pore throat radius of about 0.036 μm; below the bottom boundary of hydrocarbon accumulation, the free fluid space disappears in reservoir; the percolation capability of reservoir dies out; the potential difference inside and outside reservoir comes to zero, suggesting end of hydrocarbon accumulation, and no hydrocarbon exploration potential.