... technique. The experimental results show that the moisture content of shale is correlated with water activity using a multilayer adsorption theory. It is found that the adsorption isotherms of various shale formations can be scaled using their respective cation exchange capacity, into a single adsorption...

... to estimate the osmotic pressure resulting from an imbalance of water activities—in effect, estimating a higher mud weight needed to stabilize the well. This methodology was applied to a well drilled in the North Sea combined with mechanical wellbore-stability analysis and shows good agreement with wellbore...

... to a large difference between ion concentration (or water activity) of shale and aqueous fluids [8-10]. There are two main approaches to the investigation of interactions between shale and aqueous fluid. The first approach considers the forces acting on the clay and electrolyte system. Theoretical models...

... propagation upstream oil & gas wettability fluid pressure evaluation technique fracture propagation natural science foundation mode crack wellbore stability china net fluid pressure test sample drilling fluid in-situ stress water activity wellbore design capillary force...

... a tendency to adsorb water from drilling fluid. Using a concentrated drilling fluid, available models which are based on the ideal solution assumption fail to properly address the true shale-drilling fluid interaction. It is shown that the moisture content of shale is correlated with water activity using...

... shale gas water activity Upstream Oil & Gas mineralogy Chenevert shale sample organic-rich shale Brinell hardness bearing shale protocol complex reservoir petrophysical characterization bedding hydrocarbon bearing shale water-based fluid Reservoir Characterization fresh water...

... inside porous, clay-bearing rock. Clays are considered as semi-permeable membranes for osmotic diffusion, while the osmotic diffusion is driven by difference of water activity of shale and surrounding fluid. A new analytical solution for apparent fracture toughness as a function of water activities...

... criterion salinity drilling fluid Upstream Oil & Gas drilling fluid salinity safe salinity window instability effective principle stress failure index compressive failure osmotic pressure wellbore integrity gradient tensile failure water activity solute fracture 1. INTRODUCTION...

... Efficiency shale Brine water activity specimen osmotic pressure interaction drilling fluids and materials osmosis mechanism exposure imbalance gradient concentration shale-fluid interaction shale specimen affinity reaction osmotic theory stabilization 1. INTRODUCTION / BACKGROUND It has...

... drilling conditions. This new model reveals that there are two distinct water bodies in swelling shale. Changing stress on the platelets will change the water distribution and their water activities in these two water bodies. This model can explain observed stress sensitive activity phenomena reported...

... invading mud (upstream) and shale sample (downstream) during the tests. In the past, the results of PT tests were analyzed using a certain phenomenological model that relates the water activities of mud and shale to the specified osmotic pressure under the known shale membrane efficiency, testing...

... ABSTRACT: Experimental results are presented to show how the compressive strengths and acoustic velocities of different types of shale change when they are exposed to water-based fluids. The acoustic velocity (or slowness) and compressive strength of a soft, high water activity, Pierre I shale...

... at reasonable solutions for optimized operations and systems. Recent studies (Mody & Hale 19 Reservoir Characterization Artificial Intelligence drilling fluid formulation pore pressure water activity stability drilling fluid selection and formulation drilling fluids and materials drilling...

... for water movement. For an example, if the fluid were treated with NaC1, the concentration of ions is high in the fluid. The high concentration of ions in the drill-fluid causes a lower water activity in the fluid (the water activity equals to unity in deionized water) and an osmotic pressure difference...

... to a reference state. Thus by determining the water activities for the wellbore fluid and the shale contacted, it is possible to predict water movements. The chemical activity of the water in the wellbore can be determined using steam tables (Hill, 1969) and a relationship derived from thermodynamic properties...