查看更多>>摘要：Emulsification is a naturally occurring phenomenon during the multiphase flow. The amount of emulsion, its composition and rate of degradation can significantly affect the flow properties and subsequent oil recovery. In addition, fluid-fluid interactions were suggested as a controlling mechanism for enhancing the oil recovery by modified salinity brines. In this study, we have used high-resolution microtomography to visualise emulsions formed in heterogeneous carbonate rocks by seawater and ion-tuned brines. Additionally, interfacial tension and emulsion stability were studied in a laboratory environment to develop further understanding of the effect of naturally occurring (in absence of surfactant agents) in-situ emulsions on Enhanced Oil Recovery (EOR) at porescale. Our results show that emulsions that are formed in pores have varying compositions depending on pore geometries, wetting properties of the rock surface and ionic composition of the injected brines. In-situ emulsification has shown to be a contributing factor to the oil recovery enhancement, however, other mechanisms, such as wettability alteration plays an important role. Emulsion cluster sizes show log bimodal distribution and injection of ion tuned brines mostly contribute to improving the connectivity between the clusters and subsequent sweep efficiency of the waterflooding.
查看更多>>摘要：Despite several advances in the field of separations in hydrocyclones, achieving high separation efficiency in these devices when operating with concentrated non-Newtonian suspensions is still a challenge, and any improvement in this aspect can be a significant contribution. Thus, the objective of this study was to evaluate the behavior of a hydrocyclone operating with concentrated pseudoplastic suspensions. The device used in this study was the Maximum Overall Efficiency Hydrocyclone (MOEH), which is the result of a geometric optimization study developed by our research group whose objective was to obtain a hydrocyclone geometry that led to high separation efficiencies. The polymer carboxymethyl cellulose (CMC) was used as a rheological modulator at different concentrations. Changing the concentration of CMC in the suspension from 0.2 wt% to 1.0 wt%, it was observed reductions of 27% and 23% for the Euler number and overall efficiency of the MOEH hydrocyclone, respectively. When operating with dilute pseudoplastic suspensions (CCMC < 0.6 wt%), the drop in the separation performance could be mitigated with appropriate increments in the dimensions of the underflow diameter and reductions in the vortex finder length. Above a concentration of 0.8 wt% CMC the hydrocyclone operated as a stream splitter, with reduced efficiency of less than 2%, and the modifications in the design variables were not sufficient to reverse the detrimental effect of the increased slurry viscosity. The results obtained in this study show the relevant effect of non-Newtonian fluids in the functioning of hydrocyclones and the importance of the correct choice of geometric configurations and operating conditions to reduce the impact of the rheology in the separation performance.
查看更多>>摘要：Gel treatment is an effective way to attack excessive water production in many mature oilfields around the world. Selective penetration is desired for successful gel treatments. That is, gel materials should easily penetrate the target zones (i.e., channeling features such as superpermeable channels) without entering/damaging the nontarget zones (i.e., reservoir matrices or oil zones). This study revealed that presence of threshold penetration pressure (Delta Pth) was responsible for selective penetration behavior of tested microgels. The concept of Delta Pth was utilized to figure out favorable working conditions for effective gel treatments. Microgel dispersions were injected into superpermeable (super-k) sandpacks (mimicking super-k channels in reservoirs, 60-221 darcies), heterogeneous models with super-k channels (79-230 darcies), and sandstone cores (mimicking reservoir matrices, 50-5000 md). The results demonstrated that a minimum differential driving pressure (i.e., threshold penetration pressure, Delta Pth) was required to push microgel particles to penetrate channels or matrices. The critical penetration behavior was closely related to the particle/pore size ratio. Low Delta Pth at smaller particle/pore ratios was beneficial to allow easy penetration of gel materials into the channeling zones. On the contrary, high Delta Pth at larger particle/pore ratios was desirable to prevent gel materials from massively invading and damaging the matrices. Instead, the gel particles accumulated at the inlet surface, and a gel cake was gradually formed. The cake further prevented the invasion of the gels. The cake could be removed by chemical breakers to resume the injectivity/productivity of the matrices. Correlations were developed to describe the relationship between Delta Pth and particle/pore ratio. A distinct transition was identified at the particle/pore ratio of about 3. This work could help identify the favorable conditions to achieve successful gel treatments. In an effective conformance treatment, the particle/pore ratio in the channel should be sufficiently low to allow easy penetration of gel materials into the channel (e.g., particle/pore ratio<2 in this study). Meanwhile, the particle/pore ratio in the matrix should be large enough to support a high Delta Pth and thus prevent massive gel invasion into the matrix. This study advances the current pore scale studies (a single particle passing through a single channel) to Darcy-scale characterization.
查看更多>>摘要：A proposed modification of the Johnson-Bossler-Naumann (JBN) method incorporates capillary pressure at the inlet and outlet of a rock sample. The experimental runs are performed on Berea and Obernkriechner sandstone rock samples. Fluid is injected into Berea rock at capillary to viscous ratios 0.05, 0.1, 0.5, and 1 and into Obernkriechner rock at capillary to viscous ratios 0.05 and 0.25. Rock samples are initially saturated with 20 g/l NaCl water. The experimental observations are analyzed using classical JBN and our modified JBN. The latter's relative permeability curves are found to closely match those derived by applying history matching to a numerical model. This indicates that modified JBN can be used to provide an initial guess for history matching. We also show that accurate estimates of threshold capillary pressure are crucial to obtaining accurate oil relative permeability estimates. In contrast to those derived from the JBN method, modified JBN relative permeabilities are independent of capillary to viscous ratio or injection rate.
Wang, YulunGrammer, G. MichaelEberli, GregorWeger, Ralf...
22页
查看更多>>摘要：Rebound hardness (RHN) has become a widely applied rock mechanical parameter in the petroleum industry due to economic and convenient testing procedures. However, the RHN data can be under-utilized when lacking detailed integration with other rock properties. Targeting the unconventional "Mississippian Limestone"/STACK play in north-central Oklahoma, USA, and outcrops of the Vaca Muerta Formation in Argentina, this study aims to test the value of RHN in predicting rock properties. RHN data from the "Mississippian Limestone"/STACK cores show correlative trends with mineralogy and porosity. All the correlations show clusters by facies groups with overlaps being present among different clusters. Within these correlations, mineralogy and porosity show variable significance levels in affecting RHN among different facies groups. Leverage analysis suggests that bulk clay content and porosity exhibits the most significant control on RHN for the MISS/STACK data, with variabilities being present in different facies groups. These partitioning patterns of data by facies groups imply that facies variability affects the statistical pattern and that RHN can assist in rock typing, and hence, sample selection for detailed laboratory analyses. Forward regression analysis reveals that the confidence level of predicting porosity and sonic velocity can be enhanced using RHN. In addition to the correlative trends between RHN and rock properties, results from forward regression analysis indicate that RHN can help estimate these properties in a faster, cheaper, and non-destructive way relative to conventional laboratory analyses. Correlative trends are also observed in Vaca Muerta data, suggesting the value of RHN in characterizing similar types of mixed carbonate-siliciclastic reservoirs.
NSTL
Elsevier