东濮凹陷砂岩储层成岩作用及其对高压致密气藏的制约

DIAGENESIS OF SANDSTONE RESERVOIRS:CONSTRAINTS ON HIGH-PRESSURE TIGHT GAS DEPOSITS IN DONGPU DEPRESSION,NORTH CHINA

东濮凹陷低渗致密储层的沉积－ 成岩特征表现为砂层薄、粒度细、沉积非均质性显著；埋藏深度大于３７００ｍ ，压实作用、晚期自生伊利石－ 绿泥石和二氧化硅胶结作用强。储层具有小孔极细喉孔隙结构，表面积大，渗透率对围压的敏感性强，地下真实孔隙度和渗透率分别介于１０％ —＜ ５％ 、０．１×１０－ ３—＜ ０．００１×１０－ ３μｍ ２。研究认为，东濮凹陷致密砂岩气藏大多产出于盆地次级深洼陷中，具有高压水溶气的成因机制，这是由储层的低渗性、较高的毛细管准数、高束缚水饱和度和高温－ 高压以及充足－ 近源的天然气供给等条件所决定的。

Low-permeability and tight sandstone reservoirs in the Dongpu depression, North China, are characterized by thin layers, fine grains and evident sedimentary heterogeneity, which are buried in depth larger than 3700m with strong compaction, late-phase authigenic illite-chlorite and silica cementation. Physical properties of the sandstone reservoirs show texture of small pore and very fine pore-throat with larger surface area, lower permeability sensitive to stratigraphic confined pressure, and real porosity and permeability in buried conditions ranging in 10%—<5%, 0 1×10 -3 —<0 001×10 -3 μm 2 respectively. The high-pressure tight sandstone gas deposits mostly occur in sub-class deep-sags of the Dongpu depression. It is presented that these deposits are of high-pressure hydro-gas characteristics, which are controlled by low-permeability, high capillary number, high saturation of irreducible water, high-temperature and high-pressure condition of reservoirs, and, in another hand, abundant gas supply from near sources to a large extent.