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首页> 外文会议>SPE/AAPG/SEG Unconventional Resources Technology Conference >Assessment of Improved Oil Recovery by Osmotic Pressure in Unconventional Reservoirs: Application to Niobrara Chalk and Codell Sandstone
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Assessment of Improved Oil Recovery by Osmotic Pressure in Unconventional Reservoirs: Application to Niobrara Chalk and Codell Sandstone

机译：对非传统水库中渗透压改善的渗透压的评估：奈博拉粉笔和Codell砂岩的应用

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The ultimate oil recovery from liquid-rich unconventional reservoirs is less than ten percent, thus a great interest in developing improved oil recovery (IOR) methods that can increase oil production from such reservoirs economically. Classical waterflooding in unconventional reservoirs is not plausible because of the small pore sizes and low permeability of shale reservoirs. However, when low salinity water enters the stimulated reservoir macrofractures via the hydraulic fracture stages in shale reservoirs, an osmotic pressure gradient forms because of the salinity contrast. Even in oil-wet shale reservoirs, such osmotic pressures prevail leading to brine imbibition into the matrix and generating counter-current flow of oil into the fractures. In this paper, we present a new method to measure the osmotic pressure in core samples. The method was applied to cores from Niobrara and Codell formations in the DJ basin. The osmotic pressure leads to enhanced oil recovery (EOR) in laboratory cores and could impact EOR in shale reservoirs. Osmotic pressures, measured in low permeability shale cores, plus a precise thermodynamic calculation of the activity coefficients enabled us to calculate the ‘membrane efficiency’ of the cores. We used a highspeed centrifuge, first to saturate the cores with formation brine; second, we injected oil into the core to displace brine (1st drainage cycle); third, we allowed spontaneous imbibition of brine into the core; fourth, we conducted force imbibition displacement of the oil with brine until core reaches residual oil saturation. Because osmotic pressure is the difference between the high-salinity and low-salinity capillary pressures, the experimental process was repeated using low-salinity brine. Furthermore, we determined improved oil recovery (IOR) fraction which is the incremental oil recovered during low-salinity experiments and is a measure of IOR.
机译：来自富含液体的非传统水库的最终的石油回收率低于百分之十，因此对开发改善的石油恢复（IOR）方法有着极大的兴趣，这些方法可以经济地增加这些水库的石油生产。由于小孔尺寸和页岩储层的孔隙尺寸和低渗透性，古典水上储层的古典水上植物不合理。然而，当低盐水水通过页岩储存器中的液压断裂阶段进入刺激的储存器弧形时，由于盐度对比度，渗透压梯度形式。即使在油湿页岩储层中，这种渗透压也占据了导致盐水吸入到基质中，并产生逆流的油流入骨折。在本文中，我们提出了一种测量核心样本中渗透压的新方法。将该方法应用于DJ盆地中Niobrara和Codell形成的核心。渗透压导致实验室内核中的储油（EOR）增强，并可能影响页岩储层中的EOR。在低渗透性页岩核中测量的渗透压，以及对活动系数的精确热力学计算使我们能够计算核心的“膜效率”。我们使用了一个高速离心机，首先用地层饱和;其次，我们将油注入核心以取代盐水（第一个排水循环）;第三，我们允许自发地吸收盐水进入核心;第四，我们用盐水进行了盐水的力，直至核心达到残留的油饱和度。因为渗透压是高盐度和低盐度毛细管压力之间的差异，所以使用低盐度盐水重复实验过程。此外，我们确定了改善的采油（IOR）级分，这是在低盐度实验期间回收的增量油，并且是IOR的量度。

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