SEM and CT X-ray imaging were used to quantify the surface geometries of sandstone pore and throat networks of the oil-bearing Stanley Sandstone of the Eutaw Formation of Jasper County, Mississippi, both in dry samples and in samples that had undergone laboratory simulations of Microbial Permeability Profile Modification (MPPM) oil-recovery technology. The goal of the study was to acquire some quantified understanding of the way induced bacterial activity affected the surface geometries and impacted the porosity and permeability of the oil-bearing Stanley Sandstone. Visible porosity remained high, but significant permeability modification occurred ubiquitously with pore and throat spaces of 10 ìm – 20 μm diameter. Based upon quantitative analysis of photomicrographs, biofilm did not completely fill porosity but did clog pore throats, thus significantly impacting permeability.

The objective of this study is to characterize heterogeneity, mineralogy, and diagenetic history in the Upper Cretaceous Eutaw Formation of the Heidelberg field Jasper County, Mississippi through analysis of the Cook-McCormick-4 core. The Eutaw Formation in this interval ranges from fine-grained sandstone to siltstone. Interbedded oil-rich sandstone beds are between 1-2 in (3-5 cm) and 3ft (1 m) thick. A few intervals display consistent lithology over as much as 9 ft (3 m), however, in the majority of core beds range from 1-2 inches (3-5 cm) to 2-3 ft (0.6-1 m). Calcite is not present in oil-rich units, suggesting that oil migration impeded diagenesis. This suggests that authigenic minerals found in oil-rich units (feldspar dissolution, pyrite, quartz overgrowths, and siderite) formed prior to reservoir charging or oil emplacement. In all thin sections containing > 60% matrix, it is apparent that glauconite compaction formed pseudomatrix and green clay. The Eutaw Formation is heterogeneous and thus an excellent formation for testing enhanced oil recovery methods, such as Microbial Permeability Profile Modification (MPPM). The reservoir characterization data compiled here in can be applied to analogous units. This project is significant because it will be used to improve secondary and tertiary oil recovery efforts in oil fields located in central Mississippi.

Natural soils in work-sites are sometimes detrimental to the construction of engineering projects. Problematic soils such as soft and expansive soils are a real source of concern to the long-term stability of structures if care is not taken. Expansive soils could generate immense distress due to their volume change in response to a slight change in their water content. On the other hand, soft soils are characterised by their low shear strength and poor workability. In earthwork, replacing these soils is sometimes economically and sustainably unjustifiable in particular if they can be stabilised to improve their behaviour. Several techniques have evolved to enable construction on problematic soils such as reinforcement using fibre and planar layers and piled reinforced embankments. Chemical treatment using, e.g. lime and/or cement is an alternative method to seize the volume change of swelling clays. The use of lime as a binding agent is becoming a popular method due to its abundant availability and cost-effectiveness. When mixed with swelling clays, lime enhances the mechanical properties, workability and reduces sensitivity to absorption and release of water. There is a consensus in the literature about the primary mechanisms, namely cation exchange, flocculation and pozzolanic reaction, which cause the changes in the soil characteristics after adding lime in the presence of water. The dispute is about whether these mechanisms occur in a sequential or synchronous manner. More precisely, the controversy concerns the formation of cementitious compounds in the pozzolanic reaction, whether it starts directly or after the cation exchange and flocculation are completed. The current study aims to monitor the signs of the formation of such compounds using a geotechnical approach. In this context, the effect of delayed compaction, lime content, mineralogy composition, curing time and environmental temperature on the properties of lime-treated clays were investigated. The compaction, swelling and permeability, and unconfind compression strength tests were chosen to evaluate such effect. In general, the results of the geotechnical approach have been characterised by their scattering. The sources of this dispersion are numerous and include sampling methods, pulverisation degree, mixing times and delay of compaction process, a pre-test temperature and humidity, differences in dry unit weight values, and testing methods. Therefore, in the current study, several precautions have been set to reduce the scattering in the results of such tests so that they can be used efficiently to monitor the evolution in the properties that are directly related to the formation and development of cementitious compounds. Four clays with different mineralogy compositions, covering a wide range of liquid limits, were chosen. The mechanical and hydraulic behaviour of such clays that had been treated by various concentrations of lime up to 25% at two ambient temperatures of 20 and 40oC were monitored for various curing times. The results indicated that the timing of the onset of changes in mechanical and hydraulic properties that are related to the formation of cementitious compounds depends on the mineralogy composition of treated clay and ambient temperature. Moreover, at a given temperature, the continuity of such changes in the characteristics of a given lime-treated clay depends on the lime availability.

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