Impact of fines and rock wettability on reservoir formation damage

Abstract

Pore throat plugging of porous rock by fine particles causes formation damage, and thus has attracted attention in various areas such as petroleum engineering, hydrology and geothermal energy production. Despite significant efforts, the detailed pore‐scale mechanisms leading to formation damage and the associated permeability reduction are not well understood. We thus investigated plugging mechanisms and characteristics with a combination of ex situ (i.e., coreflooding measurements and scanning electron microscopy imaging) and in situ (i.e., nuclear magnetic resonance and μCT) methods, with a particular focus on the effect of wettability. The corefloods indicated that permeability drops rapidly when fines are injected; mechanistically thin pore throats are plugged first, followed by filling of adjacent pore bodies with the fine material (as evidenced by the nuclear magnetic resonance and μCT experiments, which can measure the pore size distribution evolution with fines injection). Furthermore, it is clear that wettability plays a major role: if fines and rock wettability are identical, plugging is significantly accelerated; wettability also controls the 3D distribution of the fines in the pore space. Furthermore we note that the deposited fines were tightly packed, apparently due to strong adhesion forces.

Well Injectivity during CO2 Geosequestration: A Review of Hydro-Physical, Chemical, and Geomechanical Effects

“…119 Besides, injectivity is further reduced if the wettability state of the rock and fines is the same. 120 Salt precipitation is another cause of fines-induced injectivity impairments through making the pores susceptible to fines entrapment by size exclusion capture in thin pore throats. 82,121,122 Mineral dissolution is also likely to increase the portion of dislodged fines in saline aquifers; however, there are some arguments on how it affects the wellbore injectivity.…”

“…121 Once the pore space is plugged, restoring the permeability is hard to achieve and might even end in well abandonment. 120,125 2.3.2. Wettability of CO 2 −Brine−Rock Systems.…”

“…Wettability alteration is among the main causes of fines migration. ,, There exists relatively small interfacial forces on the surface of strongly hydrophilic minerals, while fine particles with more CO 2 -wet surfaces are more susceptible to be detached . Besides, injectivity is further reduced if the wettability state of the rock and fines is the same …”

“…Overall, regardless of the source of fines migration, it has been demonstrated that even 0.3 wt % of detached fine particles in pore water can reduce the CO 2 injectivity by more than double the case in which TDS is 10 wt % . Once the pore space is plugged, restoring the permeability is hard to achieve and might even end in well abandonment. , …”

CO2‐Saturated Brine Injection Into Unconsolidated Sandstone: Implications for Carbon Geosequestration

“…The acid naturally reacts with various minerals in the rock, for example, albite, K‐feldspar, and glauconite (Ketzer et al, ; Lebedev, Zhang, Sarmadivaleh, et al, ; Mangane et al, ) when exposed to live brine more than 3 hr (Baker et al, ; Yasuda et al, ). Fines migration and solid reprecipitation change the pore size distribution and pore connectivity, which again significantly influence reservoir‐scale fluid dynamics (Al‐Khdheeawi et al, , ; Hangx et al, ), dramatically affect permeability (Al‐Yaseri et al, , , ; Liu et al, ; Reynolds et al, ), and storage capacity (Iglauer et al, ; Iglauer & Lebedev, ). This porosity and permeability modification thus pose a significant risk, particularly when permeability is decreased dramatically (formation damage), and as a consequence, CO 2 injectivity may be very poor (Iglauer et al, ; Lamy‐Chappuis et al, ; Mangane et al, ).…”