The study examined joint discontinuity spacing effect on drilling condition and performance in selected rocks in llorin and Ibese areas, Nigeria. Five samples for each rock type （gneiss and limestone） were tested in...The study examined joint discontinuity spacing effect on drilling condition and performance in selected rocks in llorin and Ibese areas, Nigeria. Five samples for each rock type （gneiss and limestone） were tested in the laboratory for chemical, physical and mechanical properties. Dip direction and joint spacing were measured using compass clinometers. The chemical composition was determined using X-ray Fluores- cence （XRF） spectrometer. The results show that gneiss has SiO2 of 61.88g and limestone has CaO content of 52.3g. The average dry density of gneiss and limestone are 2.6 and 2.39 g/cm^3, respectively. The uniaxial compressive strength of gneiss and limestone are 195 and 93.83 MPa, respectively. These rocks are classified as strong and moderately strong rock. Gneiss and limestone have mean joint discontinuity spacing of 0.79 and 0.25 m, which classified them as moderate and wide joint spacing respectively. Joint spacing was correlated with specific energy, bit wear and uniaxial compressive using Statistical Package for Social Science （SPSS）. The regression model has multiple coefficient of correlation of R^2 = 0.791 and R^2 =0.995 for gneiss and limestone, respectively. The variation in joint spacing could be attributed to spe- cific energy, bit wear and uniaxial compressive strength which affect drilling condition and performance. Ultimately, as joint spacing gets closer, the drilling velocity increases, drill string will be stable.展开更多
The physicochemical and microbiological assessments of thirteen accessible boreholes in Rumukalagbor in Port Harcourt were ascertained. The studies were carried out in April （onset of the rains） and June （peak of t...The physicochemical and microbiological assessments of thirteen accessible boreholes in Rumukalagbor in Port Harcourt were ascertained. The studies were carried out in April （onset of the rains） and June （peak of the rains） and the results obtained showed that all the water samples tested were acidic （pH 3.12-5.18） with the samples having lower values in June. Eight boreholes （61.5%） had high conductivity values and all boreholes recorded high TDS （total dissolved solids）.These are indications of the presence of dissolved minerals/polluting agents. TH （total hardness） values for all the borehole samples were very low （20 mg/L-60 mg/L）, which are below WHO （World Health Organization） set limit of 200 mg/L. The levels of Ca and Mg ions were determined using AAS （atomic absorption spectroscopy） and these were also observed to be very low. Ca ion concentrations were 0.15 mg/L-20.1 mg/L and Mg ion concentrations were 0.10 mg/L-10.3 mg/L. All the samples but one exceeded the WHO limit for chloride ion concentration for potable water. These high levels can account for the high pH and conductivity values and since water from some boreholes are soft, they are prone to plumbosolvacy. Sulphate and nitrate concentrations in the samples are within the WHO allowable limits. The water samples showed minimal microbial load with 38.5% not having any microbial load.展开更多
In order to investigate the permeability of porous media,it is necessary to figure out the property of wave propagation in this medium. The authors calculated the full waveforms and the 2-dimensional spectrum of fluid...In order to investigate the permeability of porous media,it is necessary to figure out the property of wave propagation in this medium. The authors calculated the full waveforms and the 2-dimensional spectrum of fluid saturated porous media,analyzed the wave propagation characteristics of different permeable stratums. From the theoretical acoustic pressure waveform received at the well-axis and the 2-D spectrum it is revealed that longitudinal-,transverse-,Stoneley-,pseudo-Rayleigh-,longitudinal mode-and transverse mode waves are different in characters in various permeable strata. Stoneley wave is sensitive to the change of permeability,and its frequency range and amplitude attenuation are influenced by permeability.展开更多
文摘The study examined joint discontinuity spacing effect on drilling condition and performance in selected rocks in llorin and Ibese areas, Nigeria. Five samples for each rock type （gneiss and limestone） were tested in the laboratory for chemical, physical and mechanical properties. Dip direction and joint spacing were measured using compass clinometers. The chemical composition was determined using X-ray Fluores- cence （XRF） spectrometer. The results show that gneiss has SiO2 of 61.88g and limestone has CaO content of 52.3g. The average dry density of gneiss and limestone are 2.6 and 2.39 g/cm^3, respectively. The uniaxial compressive strength of gneiss and limestone are 195 and 93.83 MPa, respectively. These rocks are classified as strong and moderately strong rock. Gneiss and limestone have mean joint discontinuity spacing of 0.79 and 0.25 m, which classified them as moderate and wide joint spacing respectively. Joint spacing was correlated with specific energy, bit wear and uniaxial compressive using Statistical Package for Social Science （SPSS）. The regression model has multiple coefficient of correlation of R^2 = 0.791 and R^2 =0.995 for gneiss and limestone, respectively. The variation in joint spacing could be attributed to spe- cific energy, bit wear and uniaxial compressive strength which affect drilling condition and performance. Ultimately, as joint spacing gets closer, the drilling velocity increases, drill string will be stable.
文摘The physicochemical and microbiological assessments of thirteen accessible boreholes in Rumukalagbor in Port Harcourt were ascertained. The studies were carried out in April （onset of the rains） and June （peak of the rains） and the results obtained showed that all the water samples tested were acidic （pH 3.12-5.18） with the samples having lower values in June. Eight boreholes （61.5%） had high conductivity values and all boreholes recorded high TDS （total dissolved solids）.These are indications of the presence of dissolved minerals/polluting agents. TH （total hardness） values for all the borehole samples were very low （20 mg/L-60 mg/L）, which are below WHO （World Health Organization） set limit of 200 mg/L. The levels of Ca and Mg ions were determined using AAS （atomic absorption spectroscopy） and these were also observed to be very low. Ca ion concentrations were 0.15 mg/L-20.1 mg/L and Mg ion concentrations were 0.10 mg/L-10.3 mg/L. All the samples but one exceeded the WHO limit for chloride ion concentration for potable water. These high levels can account for the high pH and conductivity values and since water from some boreholes are soft, they are prone to plumbosolvacy. Sulphate and nitrate concentrations in the samples are within the WHO allowable limits. The water samples showed minimal microbial load with 38.5% not having any microbial load.
文摘In order to investigate the permeability of porous media,it is necessary to figure out the property of wave propagation in this medium. The authors calculated the full waveforms and the 2-dimensional spectrum of fluid saturated porous media,analyzed the wave propagation characteristics of different permeable stratums. From the theoretical acoustic pressure waveform received at the well-axis and the 2-D spectrum it is revealed that longitudinal-,transverse-,Stoneley-,pseudo-Rayleigh-,longitudinal mode-and transverse mode waves are different in characters in various permeable strata. Stoneley wave is sensitive to the change of permeability,and its frequency range and amplitude attenuation are influenced by permeability.
