The effects of well damage and completion designs on geo-electrical responses in mature wellbore environments

Well integrity is one of the major concerns in long-term geologic storage sites due to its potential risk for well leakage and groundwater contamination. Evaluating changes in electrical responses due to energized steel-cased wells has the potential to quantify and predict possible wellbore failures as any kind of breakage or corrosion along highly-conductive well casings will have an impact on the distribution of subsurface electrical potential. However, realistic wellbore-geoelectrical models that can fully capture fine scale details of well completion design and state of well damage at the field scale require extensive computational effort or can even be intractable to simulate. To overcome this computational burden while still keeping the model realistic, we utilize the Hierarchical Finite Element Method which represents electrical conductivity at each dimensional component (1-D edges, 2-D planes and 3-D cells) of a tetrahedra mesh. This allows us to consider well completion designs with real-life geometric scales and well systems with realistic, detailed, progressive corrosion and damage in our models. Here, we present a comparison of possible discretization approaches of a multi-casing completion design in the finite element model. The impacts of the surface casing length and the coupling between concentric well casings, as well as the effects of the degree and the location of well damage on the electrical responses are also examined. Finally, we analyze real surface electric field data to detect the wellbore integrity failure associated with damage.

INTERPRETATION OF PRESSURE BEHAVIOR DIAGRAMS USING REMI’S STANDARD CURVES AND OTHER METHODS IN OIL WELLS

The authors analyze the dimensionless pressure and the inflow rate using Remi’s curves and other standard curves for determination of reservoir permeability and characteristics of the tested well damage and stimulation.

A new method of damage determination in geothermal wells from geothermal inflow with application to Los Humeros, Mexico

Geothermal inflow type curves were obtained for different values of well damage (i.e., inflow performance relationships). The method was evaluated by diagnosing the damage of thirteen producing wells in the Los Hu- meros, Puebla, Me?xico geothermal field. Permeability determinations were carried out for these wells and their productivity indices were estimated. Comparison of the diagnoses made via damage effects against the results of field pressure tests showed that the maximum difference between both approaches is on the order of 0.7 damage units. The methodology allows reservoir characterization along its productive life, since several production tests are carried out while the reservoir is producing. The data obtained from production tests are used to determine the damage effect and permeability of the rock formation. Previously the damage (skin factor) could only be determined from the analyses of transient pressure tests.

Dispersive Evaluation and Self-Sensing of Single Carbon Fiber/CNT-Epoxy Composites using Electro-Micromechanical Techniques

ABSTRACTSelf-sensing and interfacial evaluation were investigated with different dispersion solvents for single carbon fiber/carbon nanotube (CNT)-epoxy composites by electro-micromechanical technique and acoustic emission (AE) under loading/subsequent unloading. Optimized dispersion procedure was set up to obtain improved mechanical and electrical properties. Apparent modulus and electrical contact resistivity for CNT-epoxy composites were correlated with different dispersion solvents for CNT. CNT-epoxy composites using good dispersion solvent showed higher apparent modulus because of better stress transferring effect due to relatively uniform dispersion of CNT in epoxy and enhanced interfacial adhesion between CNT and epoxy matrix. However, good solvent showed high apparent modulus but low thermodynamic work of adhesion, Wa for single carbon microfiber/CNT-epoxy composite. It is because hydrophobic high advanced contact angle was shown in good solvent, which can not be compatible with carbon microfiber well. Damage sensing was also detected simultaneously by AE combined with electrical resistance measurement. Electrical resistivity increased stepwise with progressing fiber fracture due to the maintaining numerous electrical contact by CNT.

Seismic Capacity Requirements for Low-Rise Reinforced Concrete Buildings Comprised of Members Failing in Shear and in Flexure

This paper presents a method for determining required shear and flexural strengths associated with structural damage states for various levels of earthquake demand of low-rise RC buildings having a dual lateral-load resisting system. The interaction curves of the required strengths are derived for various ductility ratios based on nonlinear dynamic analyses of the singledegree- of-freedom system. Damage states of buildings controlled by both shear and flexure are evaluated by the procedure outlined by the Japanese Standard. The proposed method predicts reasonably well damage sustained by actual buildings during an earthquake. The proposed method can be used to develop performance-based seismic evaluation and rehabilitation procedures of lowrise RC buildings having a dual lateral-load resisting system.