In order to develop the unused Chang8 and Chang9 reservoirs reasonably and efficiently,it is necessary to establish a set of reasonable well pattern system to accumulate experience and guide the efficient and reasonable development of other deep oil-bearing areas in Wuqi Oilfield.According to the correlation between well pattern density and recovery efficiency under different mobility,the well pattern density of Chang8 and Chang9 reservoirs in the study area is 6.8 wells/km2.In fact,the well pattern density of the developed Triassic oilfield in the west of Yanchang Oilfield is 9.2～18.0 wells/km2.Considering the connection of new and old well patterns,it is determined that the development well pattern density of Chang8 and Chang9 reservoirs should be 10～15 wells/km2 and the well pattern density deployed at 300 m well spacing is more suitable.On the basis of the analysis of the maximum principal stress and fracture orientation in the study area,the well pattern plan is deployed on the basis of the original 300 m～300 m square well pattern as far as possible to inherit the original well pattern.300× 300 square reverse nine-point well layout is adopted,and the reverse nine-point water injection is adopted.The above results have certain guiding value to the development of deep reservoir in Wuqi oilfield.
针对裂缝性油藏渗流规律复杂,目前暂无有效的方法进行描述这一问题,以实际露头为原型开展裂缝精细描述,得到不同尺度裂缝符合幂函数分布规律,且裂缝尺度越小,数目越多.在此基础上建立裂缝精细表征地质模型,开展裂缝油藏渗流规律研究.结果表明:开采初期油藏中大裂缝优先得到动用,产油比例95％以上来自大裂缝,此阶段油藏含水率一般不超过20％,生产特征表现为产能高和递减快;随着注入水沿大裂缝窜流,油藏含水上升,中裂缝在大裂缝的带动下控制油藏整个渗流场和剩余油的分布,裂缝出油比例仍占70％以上,油藏含水率为20％～40％;当大、中裂缝水淹后,油藏含水率超过40％,在渗吸作用下小裂缝及基质成为产油的关键,占比达50％以上,这一阶段油藏采油速度低但持续时间长.根据不同阶段的渗流规律制定合理的注水开发策略,以减缓裂缝水窜和增大基质出油,具体为初期阶段降压开采延长无水采油期,中期阶段脉冲注水减缓裂缝水窜,后期阶段周期注水增加基质出油.该注水策略在渤海KAT油田现场应用,实践效果较好,单井含水率下降10％～60％,日增油10～90 m3,提高采收率超过6％,可为类似裂缝性油藏注水开发提供指导和借鉴.
为了摸清富县地区长7页岩油气富集特征与主控因素,以富县地区长7页岩油气勘探实践为基础,结合前人的研究成果,通过分析成藏地质背景、页岩层系内部油气运聚特征以及页岩油气富集特征及模式,对油气富集主控因素进行研究,研究结果表明:1)长7砂岩油藏类型主要为透镜体油藏和上倾尖灭型油藏,已发现油藏主要分布在长7顶部,在研究区东部长7底部发育少量油藏;纵向上烃源岩底部、顶部的砂体、夹在两套烃源岩中间的砂体往往是有利的勘探目标.2)平面上,在研究区中西部长7油藏主要沿三角洲前缘砂体的环古湖岸线、主分流河道分布,在研究区东部油藏主要分布于位于流线汇聚区及流线与砂体大角度相交区域.3)总体来看,页岩段中部、中下部油气含量要高于页岩段上部的油气含量.影响页岩油气含量的因素复杂,主要有TOC、有机质成熟度、黏土矿物含量、孔隙及孔隙结构等,该成果为富县地区长7页岩油气下一步的高效开发,具有一定的指导意义.
According to the difficulty in dynamic reserves prediction induced by the low pressure, high adsorbed gas content and hard pressure-up test of continental shale gas in Yan ’an Area, this paper use the gas percolation theory and reservoir engineering method to establish a flow material balance model suitable for the calculation of dynamic reserves of continental shale gas in Yan’an Area on the basis of traditional flow mass balance method. Furthermore, combined with actual production data, the dynamic reserves of actual continental shale gas wells are evaluated. The results showed that: 1) The traditional flow mass balance method ignores the variations of gas compression coefficient（C g ） and viscosity（μ g ） during the production process, which are very significant under the conditions of low pressure and high adsorption capacity of continental shale gas in Yan ’an Area; 2) Ignoring the change of μ g C g and the desorption effect of adsorbed gas during the step-down process of shale gas will lead to a low predicted dynamic reserve; 3) Taking a continental shale gas well in Yan ’an Area as an example, the dynamic reserves of this well are predicted to be 2.2×10~7 m~3 by using the established method, which is 10% higher than that of the traditional method. Meanwhile, it also shows that the area where the well is located has certain development prospects. The study has important guiding significance for the production system and production prediction of terrestrial shale gas in Yan’an Area.
The Chang7 member of Yanchang Formation is an important organic-rich shale stratum developed in the Ordos Basin, yet no breakthrough has been achieved for shale gas exploration and development. To study the pore types and adsorption characteristics of continental mud shale in Chang7 member of Yanchang Formation of Yan’an Area, core samples from the Yan′an Area were analyzed using a series of methods, including organic geochemistry, XRD, FE-SEM, nitrogen adsorption and isothermal adsorption of high-pressure methane. The results show that the thickness of the mud shale of the Chang7 member of Yanchang Formation in Yan’an Area（the average thickness is 70～80 m）, larger high abundance of organic matter（the average of TOC is 4.89%）, the thermal evolution of the mud shale maturity belongs to the mature stage（the average R o 0.90%）, organic matter type is given priority to with typeⅡ. The mineral composition of mud shale is mainly clay minerals and quartz, with the highest clay minerals（mass fraction is 30%～63%, the average is 47.52%） and lower quartz mass fraction content（the average is 27.56%）.The mud shale pores in Chang7 member of Yanchang Formation are of various types, mainly intergranular pores and intrarenal pores, followed by intergranular pores, microfractures, dissolution pores and organic matter pores, providing storage space for shale gas. The maximum adsorption capacity of methane in mud shale under different temperature conditions is 0.71～6.49 m~3/t, with an average is 3.325 m~3/t, and that shows strong adsorption capacity for shale gas. The adsorbed gas quantity is positively correlated with clay mineral content, specific surface area, total pore volume TOC and R o . As the degree of thermal evolution increases, the pore network system of shale changes from inorganic pores to organic pores, which is conducive to enhancing the adsorption of mud shale.
