Historically, the offshore Mancos play of the San Juan Basin has produced oil from noncommercial to marginally commercial reservoirs consisting of dark-gray marine shale with thin beds and laminae of fine-grained sandstone of limited permeability. During the last decade, horizontal drilling with horizontal wells has resulted in substantially increased production. However, placement of the offshore Mancos play within the Mancos total petroleum system has been poorly understood. Here, the offshore Mancos play is interpreted as a carrier bed play within the Mancos total petroleum system.Unconventional reservoirs of the offshore Mancos play are stratigraphically equivalent to updip conventional reservoirs deposited nearer to the shoreline and to downdip source rocks matured to peak oil generation. Offshore Mancos facies include a proximal facies to the southwest, a medial facies, and a distal facies to the northeast. Oil production has been obtained from the proximal and medial facies.Mancos shales contain oil-generative kerogens that are within the upper oil window near conventional reservoirs in the south and have matured to peak oil generation downdip of and to the northeast of the offshore Mancos reservoirs. Uniform API gravities of light sweet produced oils that transcend thermal maturity variations of Mancos shales indicate that oils generated in downdip mature source rocks migrated updip through the carrier bed sandstones of the offshore play and into the conventional reservoirs. Residual oil saturations are consistent with the concept of migrating oils moving updip through only a small number of interconnected pathways within a carrier bed.

中文翻译：

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位于圣胡安盆地的离岸 Mancos 油田是 Mancos 总石油系统的一个组成部分

从历史上看，圣胡安盆地的海上 Mancos 油藏从非商业性到商业性的油藏中生产石油，这些油藏由深灰色海相页岩和薄层和渗透率有限的细粒砂岩层组成。在过去的十年中，水平井的水平钻井大大提高了产量。然而，人们对 Mancos 海上作业在 Mancos 总石油系统中的位置知之甚少。在这里，离岸 Mancos 油藏被解释为 Mancos 总石油系统内的载体床层。离岸 Mancos 油藏的非常规储层在地层上相当于沉积在更靠近海岸线的上倾常规储层和下倾烃源岩成熟到产油高峰。近海 Mancos 相包括西南近端相、中部相和东北相远端相。近中相已获得石油生产。 Mancos 页岩包含产油干酪根，位于南部常规储层附近的上部油窗内，并且已经成熟到海上 Mancos 储层下倾和东北部的产油高峰. 超越曼科斯页岩热成熟度变化的轻质低硫产出油的均匀 API 重力表明，在下倾成熟烃源岩中生成的油向上倾移通过海上作业的载体床砂岩并进入常规储层。