Water imbibition of shale and its potential influence on shale gas recovery—a comparative study of marine and continental shale formations

Abstract

a b s t r a c tA large volume of fracturing fluid is pumped into a well to stimulate shale formation. The water is imbibed into the reservoir during this procedure. The effect of the imbibed water on gas recovery is still in debate. In this work, we study the spontaneous imbibition of water into marine shale samples from the Sichuan Basin and continental shale samples from Erdos Basin to explore the fluid imbibition characteristics and permeability change during water imbibition.Comparison of imbibition experiments shows that shale has stronger water imbibition and diffusion capacity than relatively higher permeability sandstone. Once the imbibition stops, water in shale has stronger ability to diffuse into deeper matrix, the water content in the main flow path decreases.Experiments in this study show that marine shale has stronger water imbibition capacity than continental shale. The permeability of continental shale decreases significantly with increasing imbibition water volume; however, the permeability of marine shale decreases at first and increases after a certain imbibition time. The induced fracture is obvious in the marine shale. SEM analysis shows that the relationship between the clay mineral and organic matter of continental shale is much more complex than that of marine shale, which may be the key factor restricting the water imbibition because the flow path is trapped by swelled clay minerals.Through this study, we concluded that whether gas recovery benefits from water imbibition depends on three aspects: 1) the diffusion ability of liquid into matrix; 2) the new cracks introduced by imbibed water; and 3) the formation sensibility. This study is useful for optimizing fracture fluids and determining the best flow-back method.

Mathematical Model for the Fluid-Gas Spontaneous Displacement in Nanoscale Porous Media considering the Slippage and Temperature

“…The linear relationship is evident, and the parameters and can easily be derived in Figure 2. The results from linear fitting (see (10) and (11)) are shown in Table 2. Fluid viscosity reflects the ability of resistance of fluid to gradual deformation by shear stress or tensile stress.…”

“…In this process, water will be imbibed into matrix in the fractured reservoir by many influences, including capillary pressure [3][4][5], chemical osmotic pressure [6], pore network [7][8][9], and clay mineral [10], which is called spontaneous imbibition. Also, leakage, lost circulation, and induced fracture in drilling process will lead to fracturing fluid being pumped into formation [11][12][13], which will also cause imbibition process and may change the stress field near wellbore [14] and drilling state [15,16].…”

Spontaneous imbibition in asymmetric branch-like throat structures in unconventional reservoirs

“…Blocked fracturing liquid in pore structures is critical for gas production (Yuan et al, 2015a(Yuan et al, , 2015bMoghanloo et al, 2015). The ability of liquid imbibition, liquid diffusing and self-unblocking is critical to the successful development of shale gas reservoirs (Shen et al, 2016).…”

Impact of Petrophysical Properties on Hydraulic Fracturing and Development in Tight Volcanic Gas Reservoirs

“…APT is caused by fluid filtrating into the formation to reduce the formation permeability [4][5][6]. However, after the well has been shut-in for some time, the permeability of volcanic reservoirs increases and the APT can be autoremoved to some extent, similar to gas shale [7,8]. The combination of applying multilateral horizontal drilling and multistage hydraulic fracturing has successfully unlocked unconventionally tight hydrocarbon reservoirs.…”