四种不同二氧化碳注入方案对储层压力和饱和度的影响

xinmeng

四种不同二氧化碳注入方案对储层压力和饱和度的影响

Ager,2018, 2(3): 305-318

原文网址：http://www.astp-agr.com/index.php/Index/Index/detail?id=74

  本研究探讨了四种不同的注入方案（一.恒速，二.逐步增长率，三.逐步递减率，以及四.循环速率），都受二氧化碳注入累积量的限制，二氧化碳的注入会影响到压力恢复的可能程度和二氧化碳羽流，它们在评价二氧化碳储存场所的环境风险性能方面起着重要作用。这一目标是通过一个具有代表性的模型来实现的，该模型是由多层具有极强的渗透性（渗透率介于1至2达西之间）砂岩组成的，并由横向延伸的零星间断的薄层页岩隔开，以穿孔的形式出现。

结果表明，循环注入倾向于保持孔隙压力低于其他三种注入方案，而在整个注入周期（50年）内，其压力上升幅度最大并呈逐步递减趋势。在注入30年后，二氧化碳的压缩性在减少波动的循环注入信号对压力的影响方面起着一定的作用，而在成分混杂的情况下，这一时间减少了5年。除了循环注入方案之外，所有其他三种注入方案导致几乎相同幅度和面积的二氧化碳饱和度，而在循环注入的情况下它表现出循环行为。在均质和成分混杂的情况下，主要的观察结果都是相似的，尽管代表性的点的分层异质性带来了结果上的细微差异。研究结果表明，在储集层中采用循环注入方案储存二氧化碳是较好的方法，因为由于地质原因，在注入过程中可能容易出现高压聚积（如裂缝性页岩储层）。这些结果对利用二氧化碳提高采收率（EOR）也有重要意义，其主要目的是通过增加孔隙压力来驱油；对于利用二氧化碳提高采收率，逐步递减速率最好，因为它会最大的增加孔隙压力。

Impact of four different CO2 injection schemes on extent of reservoir pressure and saturation

Harpreet Singh

(Published: 2018-07-14)

CorrespondingAuthor and Email: Harpreet Singh, harpreet.singh@netl.doe.gov

---

Citation: Singh, H. Impact of four different CO2 injection schemes on extent of reservoir pressure and saturation. Advances in Geo-Energy Research, 2018, 2(3): 305-318, doi: 10.26804/ager.2018.03.08.

---

ArticleType: Original article

---

Abstract：

    This study investigates how four different injection schemes, (i. constant rate, ii. stepwise increasing rate, iii. stepwise decreasing rate, and iv. cyclic rate), constrained by the cumulative amount of CO2 injected, affect the likely extent of pressure buildup and CO2 plume, which play a role in the appraisal of environmental risk performance at CO2 storage sites. This objective is achieved using a representative model of a realistic site consisting of multi-layer sandstone that is extremely permeable (between 1 to 2 Darcy) and separated by thin layers of shale extending laterally with sporadic discontinuities in form of perforations.

Results show that cyclic injection tends to keep the pore pressure lower than the other three injection schemes, while the highest pressure increase over the entire injection period (50 years) is observed with stepwise decreasing rate. The compressibility of CO2 plays a role in attenuating the impact of fluctuating cyclic injection signals on pressure after 30 years of injection, where this time decreases by 5 years in case of heterogeneous scenario. Except for the cyclic injection scheme, all other three injection schemes lead to almost the same magnitude and areal extent of CO2 saturation, while it shows a cyclic behavior in the case of the cyclic injection. Major observations are similar in both homogeneous and heterogeneous scenarios, although layered heterogeneity in the representative site introduces small differences in results. The results imply that it would be preferable to store CO2 using a cyclic injection scheme in storage reservoirs that may be prone to high pressure buildup during injection because of their geology (e.g. fractured shale reservoirs). These results also carry important implications for enhanced oil recovery (EOR) using CO2 where the primary goal is to drive the oil out by increasing pore pressure; for EOR by CO2 , stepwise decreasing rate would be most preferable as it leads to highest increase in pore pressure.

---

Keywords: Pressure buildup, compressibility, injection schemes, storage, EOR.