The Experts below are selected from a list of 153 Experts worldwide ranked by ideXlab platform

Andrew K. Wojtanowicz - One of the best experts on this subject based on the ideXlab platform.

  • pressure buildup test analysis in wells with sustained casing pressure
    Journal of Natural Gas Science and Engineering, 2017
    Co-Authors: R Xu, Andrew K. Wojtanowicz
    Abstract:

    Abstract When the well's casing head pressure cannot be permanently bled off with a needle valve, the casing is said to exhibit Sustained Casing Pressure (SCP). Rebuilding of surface pressure (pressure buildup – after closing the valve) results from migration of gas in the leaking cement sheath of the well's annulus. Problem of sustained casing pressure (SCP) has been widespread in the Gulf of Mexico and also reported in Canada, Norway, and other places. Regulations require 24-hr testing of SCP wells comprising pressure bleed-down followed with pressure buildup. In these tests, the rate of pressure buildup is indicative of the size of cement leak – prompt buildup implies larger leak on a relative scale with no quantification. Presented here is the first mathematical model for quantitative analysis of pressure buildup in SCP wells. The model simplifies transient gas flow in cement and ignores migration time of gas in the Annular Fluid column above the cement top. The simplification allows finding the size of cement leak and the depth and value of gas pressure source formation. Also presented is validation of the model with actual field data from testing SCP wells. Matching the model to field data gives acceptable estimates of the gas-source formation depth and pressure, cement leak size, and expected maximum casing pressure value. The results also reveal a correlation between the pressure buildup-stabilization pattern and well parameters - cement leak size controls the pressure buildup rate, while the gas-source formation pressure controls the stabilized pressure value. Quantitative analysis of SCP buildup with the new model could be extremely useful as it provides values of three parameters (cement leak size, gas source formation depth and pressure) that are critically important for designing remedial treatment.

  • pilot size process visualization gravity Fluid displacement method to stop Annular gas migration
    Journal of Natural Gas Science and Engineering, 2016
    Co-Authors: Efeca Demirci, Andrew K. Wojtanowicz
    Abstract:

    Abstract Irreducible casing pressure, also known as Sustained Casing Pressure (SCP), cannot be bled off as it is caused by late gas migration in the Annular Fluid column above the top of leaking cement. The leaking cement problem is widely spread as shown in statistics from Gulf of Mexico, Canada, Norway and other places where SCP has been regulated. The regulations require removal of severe SCP to continue well's operation and removal of any SCP prior to well's plugging and abandonment (P&A). Typically, SCP removal requires either downhole intervention or Annular intervention methods. The latter method involves displacing the Annular Fluid above the top of the gas-leaking well cement with a heavy Fluid to increase the hydrostatic pressure and stop the gas leak. Past field applications of the method failed – most likely due to incompatibility of the two Fluids. In this study, a see-through scaled-down hydraulic analog of the well's annulus was designed based on a population of typical annulus sizes and used for video-taped displacement experiments with clear synthetic-clay muds and heavy (kill) Fluids. The results show that miscible combination of the two Fluids mix at the contact and show poor displacement. However, immiscible hydrophobic kill Fluids settle rapidly in the Annular Fluid and provide more effective displacement. The study demonstrates importance of controlled injection of the kill Fluid by adjusting the rate and nozzle size to set out efficient buoyant settling and prevent initial dispersion. The results also show that horizontal injection is superior to vertical injection as the impingement effect increases the efficiency of the displacement process. A side- (versus top-) injection geometry and the injection rate data are analyzed to develop empirical correlation of maximum injection rate for a given properties of the two Fluids.

Weihsin Liao - One of the best experts on this subject based on the ideXlab platform.

  • a magnetorheological valve with both Annular and radial Fluid flow resistance gaps
    Smart Materials and Structures, 2009
    Co-Authors: Daihua Wang, Weihsin Liao
    Abstract:

    In order to increase the efficiency of magnetorheological (MR) valves, Ai et al (2006) proposed an MR valve simultaneously possessing Annular and radial Fluid flow resistance channels with the assumption that the magnetic flux densities at the Annular and radial Fluid flow gaps are identical. In this paper, an MR valve simultaneously possessing Annular and radial Fluid flow resistance channels is designed, fabricated, modeled and tested. A model for the developed MR valve is produced and its performances are theoretically predicted based on the average magnetic flux densities in the Annular and radial Fluid flow gaps through finite element analysis. The theoretical results for the developed MR valve are compared with the experimental results. In addition, the performances of the developed MR valve are theoretically and experimentally compared with those of the MR valve with only Annular Fluid flow gaps. It has been shown that the theoretical results match well with the experimental results. Mainly attributed to the radial Fluid flow gaps, the pressure drops across the MR valve with both Annular and radial Fluid flow gaps are larger than those across the MR valve with only Annular Fluid flow gaps for varying valve parameters. The radial Fluid flow gaps in the MR valve can reach a higher efficiency and larger controllable range than those by Annular Fluid flow gaps to some extent.

  • design and modeling of a magnetorheological valve with both Annular and radial flow paths
    Journal of Intelligent Material Systems and Structures, 2006
    Co-Authors: Daihua Wang, Weihsin Liao
    Abstract:

    In this article, an MR valve possessing simultaneously Annular Fluid flow resistance channels and radial Fluid flow resistance channels is designed, and its structure and working principle are described. In addition, a mathematical model for the MR valve with both Annular and radial flow paths is developed and the simulation is carried out to evaluate the newly developed MR valve. The simulation results based on the proposed model indicate that the efficiency of the MR valve with circular disk-type Fluid resistance channels is superior to that with Annular Fluid resistance channels under the same magnetic flux density and outer radius of the valve. Furthermore, the results also show that the efficiency of the MR valve can be improved significantly with two types of Fluid flow resistance gaps, viz. Annular Fluid flow resistance gaps and circular disk-type Fluid flow resistance gaps simultaneously.

Daihua Wang - One of the best experts on this subject based on the ideXlab platform.

  • a magnetorheological valve with both Annular and radial Fluid flow resistance gaps
    Smart Materials and Structures, 2009
    Co-Authors: Daihua Wang, Weihsin Liao
    Abstract:

    In order to increase the efficiency of magnetorheological (MR) valves, Ai et al (2006) proposed an MR valve simultaneously possessing Annular and radial Fluid flow resistance channels with the assumption that the magnetic flux densities at the Annular and radial Fluid flow gaps are identical. In this paper, an MR valve simultaneously possessing Annular and radial Fluid flow resistance channels is designed, fabricated, modeled and tested. A model for the developed MR valve is produced and its performances are theoretically predicted based on the average magnetic flux densities in the Annular and radial Fluid flow gaps through finite element analysis. The theoretical results for the developed MR valve are compared with the experimental results. In addition, the performances of the developed MR valve are theoretically and experimentally compared with those of the MR valve with only Annular Fluid flow gaps. It has been shown that the theoretical results match well with the experimental results. Mainly attributed to the radial Fluid flow gaps, the pressure drops across the MR valve with both Annular and radial Fluid flow gaps are larger than those across the MR valve with only Annular Fluid flow gaps for varying valve parameters. The radial Fluid flow gaps in the MR valve can reach a higher efficiency and larger controllable range than those by Annular Fluid flow gaps to some extent.

  • design and modeling of a magnetorheological valve with both Annular and radial flow paths
    Journal of Intelligent Material Systems and Structures, 2006
    Co-Authors: Daihua Wang, Weihsin Liao
    Abstract:

    In this article, an MR valve possessing simultaneously Annular Fluid flow resistance channels and radial Fluid flow resistance channels is designed, and its structure and working principle are described. In addition, a mathematical model for the MR valve with both Annular and radial flow paths is developed and the simulation is carried out to evaluate the newly developed MR valve. The simulation results based on the proposed model indicate that the efficiency of the MR valve with circular disk-type Fluid resistance channels is superior to that with Annular Fluid resistance channels under the same magnetic flux density and outer radius of the valve. Furthermore, the results also show that the efficiency of the MR valve can be improved significantly with two types of Fluid flow resistance gaps, viz. Annular Fluid flow resistance gaps and circular disk-type Fluid flow resistance gaps simultaneously.

R Xu - One of the best experts on this subject based on the ideXlab platform.

  • pressure buildup test analysis in wells with sustained casing pressure
    Journal of Natural Gas Science and Engineering, 2017
    Co-Authors: R Xu, Andrew K. Wojtanowicz
    Abstract:

    Abstract When the well's casing head pressure cannot be permanently bled off with a needle valve, the casing is said to exhibit Sustained Casing Pressure (SCP). Rebuilding of surface pressure (pressure buildup – after closing the valve) results from migration of gas in the leaking cement sheath of the well's annulus. Problem of sustained casing pressure (SCP) has been widespread in the Gulf of Mexico and also reported in Canada, Norway, and other places. Regulations require 24-hr testing of SCP wells comprising pressure bleed-down followed with pressure buildup. In these tests, the rate of pressure buildup is indicative of the size of cement leak – prompt buildup implies larger leak on a relative scale with no quantification. Presented here is the first mathematical model for quantitative analysis of pressure buildup in SCP wells. The model simplifies transient gas flow in cement and ignores migration time of gas in the Annular Fluid column above the cement top. The simplification allows finding the size of cement leak and the depth and value of gas pressure source formation. Also presented is validation of the model with actual field data from testing SCP wells. Matching the model to field data gives acceptable estimates of the gas-source formation depth and pressure, cement leak size, and expected maximum casing pressure value. The results also reveal a correlation between the pressure buildup-stabilization pattern and well parameters - cement leak size controls the pressure buildup rate, while the gas-source formation pressure controls the stabilized pressure value. Quantitative analysis of SCP buildup with the new model could be extremely useful as it provides values of three parameters (cement leak size, gas source formation depth and pressure) that are critically important for designing remedial treatment.

Qing Wang - One of the best experts on this subject based on the ideXlab platform.

  • Impact of wellbore Fluid properties on trapped Annular pressure in deepwater wells
    Petroleum Exploration and Development, 2016
    Co-Authors: Bo Zhang, Zhichuan Guan, Yanan Sheng, Qing Wang
    Abstract:

    Abstract To reduce the threat of trapped Annular pressure on deepwater wells safe production, this study established a model of calculating trapped Annular pressure, examined the influence of wellbore Fluid properties on trapped Annular pressure, and analyzed the sensitivities and engineering feasibilities of controllable factors. To realize the calculation of trapped Annular pressure under multiple annuli with liquid, a volume balance equation set was built according to compatibility principle and a wellbore temperature computing model was built based on wellbore-formation coupled heat transfer. Annular pressure decreases as the expansion-compression ratio of Annular Fluid reduces. Decreasing Annular saturation can eliminate Annular pressure radically and then a formula was proposed to give extreme Annular saturation. The increase of production Fluid specific heat capacity and flow rate leads to enhancement of Annular pressure. Annular pressure keeps a linear relation to production Fluid hole bottom temperature and the wellhead temperature can reflect the value of Annular pressure. The water ratio increase of production Fluid causes dynamic increase of Annular pressure. The sensitivity of Annular saturation is much higher than other factors. Decreasing Annular liquid thermal conductivity has relatively higher engineering feasibility. The Annular pressure can be controlled effectively by developing subsea wellheads with the ability to release Annular Fluid, highly compressible materials and downhole thermal-insulated Fluids.

  • Impact of wellbore Fluid properties on trapped Annular pressure in deepwater wells
    KeAi Communications Co. Ltd., 2016
    Co-Authors: Bo Zhang, Zhichuan Guan, Yanan Sheng, Qing Wang
    Abstract:

    To reduce the threat of trapped Annular pressure on deepwater wells safe production, this study established a model of calculating trapped Annular pressure, examined the influence of wellbore Fluid properties on trapped Annular pressure, and analyzed the sensitivities and engineering feasibilities of controllable factors. To realize the calculation of trapped Annular pressure under multiple annuli with liquid, a volume balance equation set was built according to compatibility principle and a wellbore temperature computing model was built based on wellbore-formation coupled heat transfer. Annular pressure decreases as the expansion-compression ratio of Annular Fluid reduces. Decreasing Annular saturation can eliminate Annular pressure radically and then a formula was proposed to give extreme Annular saturation. The increase of production Fluid specific heat capacity and flow rate leads to enhancement of Annular pressure. Annular pressure keeps a linear relation to production Fluid hole bottom temperature and the wellhead temperature can reflect the value of Annular pressure. The water ratio increase of production Fluid causes dynamic increase of Annular pressure. The sensitivity of Annular saturation is much higher than other factors. Decreasing Annular liquid thermal conductivity has relatively higher engineering feasibility. The Annular pressure can be controlled effectively by developing subsea wellheads with the ability to release Annular Fluid, highly compressible materials and downhole thermal-insulated Fluids. Key words: deepwater wells, Annular pressure, Fluid properties, Annular Fluid, extreme Annular saturatio