Investigation into the Classification of Tight Sandstone Reservoirs via Imbibition Characteristics

Abstract

Tight sandstone reservoirs are often produced by shutting in the well and inducing imbibition. However, by adopting current reservoir classifications, the heterogeneity of reservoirs cannot be properly treated. Based upon the analysis of the imbibition curves and mercury intrusion porosimetry tests, Chang-7 tight sandstone reservoirs were classified into three categories according to the newly proposed standards. Imbibition tests demonstrated that for the first category, imbibition and drainage occurred continuously and never reached the plateau within the experiment duration. It was suggested that a longer shut-in time favors the production of oil. For the second category, a steady state for imbibition was reached and a shut-in time as short as three days resulted in a high imbibition rate. For the third category, a plateau was reached for the first time and imbibition restarted until a steady state was reached. The average shut-in time for the third category was eight days. Compatibility between reservoir characteristics and a soaking development regime based upon the proposed classification methods effectively enhances the oil recovery efficiency of formations with distinct petrophysical properties. This provides insight into the classification methods of tight sandstone reservoirs.

Unconventional hydrocarbon resources: geological statistics, petrophysical characterization, and field development strategies

“…It may also consist of siltstone, silty sandstone, dolomites, and argillaceous limestones (Speight 2017). These formations are associated with high heterogeneities, have a complex pore structure system, and relatively low potential for a natural drive (Li et al 2018). These complex pore structures are the combination of various small to very small pores resulting from several processes such as the fine-grained sediments deposition, postdepositional diagenesis altering the original structure of pores, and the presence of different clay and shale minerals in the pores (Rushing et al 2008).…”

A Molten-Salt Pyrolysis Synthesis Strategy toward Sulfur-Functionalized Carbon for Elemental Mercury Removal from Coal-Combustion Flue Gas

“…The excessive emission of mercury from industrial activities has caused consequential hazards to the ecosystem and human health [1][2][3]. Coal combustion is one of the largest industrial sources of mercury emission.…”

Differences in Imbibition Efficiency Between Bedding and Tectonic Fractures in the Lucaogou Formation in the Jimusar Sag: Evidence From Simulation Experiments

“…Spontaneous imbibition can be seen in two ways. On the one hand, the change curve of imbibition over time can be used to describe its process (Li et al, 2018). Gu et al (2017) found that with the increase in the rate of fluid imbibition (volume of liquid/unit of time), the spontaneous imbibition recovery efficiency which is defined as the amount of oil that is recovered after the spontaneous imbibition occurred compared to original reservoir reserves is improved.…”

“…However, Peng et al (2010) showed that when the spontaneous imbibition rate is greater than a certain value, the improvement of spontaneous imbibition recovery will slow down or stabilize. Li et al (2018) proposed that with the increase in interfacial tension, the thickness of spontaneous imbibition film first increases and then decreases. On the other hand, the control factors of spontaneous imbibition were explored.…”