Physics Test - Lab Report Example

Theory 1 Explain the physical principle of the tools for: a. SP log The Spontaneous Potential log is sensitive to electrical charge. In this same regard, it functions by measuring electrical potentials between depths in oil boreholes together with a voltage exhibited on the surface. Hydrocarbon suppression reduces the response which can be realized by the SP log. b. GR log The Gamma Ray log uses gamma radiation to measure the characteristics of rocks or sediments in a well. It functions well even in steel or concrete walls because of it being sensitive. c. Density log This type of log is majorly attributed to its sensitivity to porosity. This is the property which enables it to function the way it does. It is able to determine the porosity of materials through the process of Compton scattering. In this case, interaction of electrons with gamma rays leads to the scattering. d. Litho-density log This type of log measures the photoelectric absorption cross section and the bulk density. Gamma ray source and scintillation detectors are used to record this measurement. e. Neutron density log This log measures the density of hydrogen which is in a reservoir. In this case, a neutron cloud is measured. This is done at varying energy levels in the given volume. f. NMR log This is a logging approach which makes use of the Nuclear Magnetic Resonance for the purpose of establishing permeability and porosity. This is achieved through the creation of a magnetic field 1.2 What parameters or rock properties are plot in the above logs? What units and scales do they use? From the above discussions, it is evident that there are some rock properties which are exhibited. They include permeability, porosity and magnetism. 2. What factors affect (and how) a. SP log? The Sp log is affected by Hydrocarbon suppression which limits the way the log will respond and provide feedback b. GR log? The GR log is affected by the density of the materials under which it is functioning. For example, if the steel or concrete is very thick, its functionality may be impaired. c. Density log? This is affected by electron intensity. If for example the intensity of the electrons is significantly high, there may be a lot of scattering which may produce a result which is far from what is expected. d. Litho-density log? This may be significantly affected by the cross sectional area which is being measured. If the area is too large, the measurement may not be done accurately. e. Neutron density log? The energy levels which are in the volume can cause an effect on the measurements recorded by this log. This effect may be in terms of an increase in the recorded values or even a decrease. f. NMR log? The intensity of the magnetic field is an important factor to consider in this case. An extremely strong or weak magnetic field may influence the porous or permeability recording. 3. List the applications of a. SP log This log is used to the salinity associated with water formation. It is also used for the detection of permeable beds. b. GR log It is used to establish well-to-well correlations and the quantitative evaluation of shaliness. c. Density log This establishes the correlation of density in a well, it also determines the photoelectric factor therein. The thickness of the mudcake is also established in the process d. Litho-density log This is used to estimate the formation porosity and the formation density. Through the use of the litho-density the fluid type can also be established. The pore space of the oil and gas is also measured through the litho-density log. e. Neutron density log This is used to determine borehole temperature and pressure, borehole salinity, mud weight and borehole size. f. NMR log? This measures the magnetic content of hydrogen. The permeability of hydrocarbons is also established with the use of the NMR log. 5. What is apparent porosity? This refers to the amount of pores that are in a volume of a solid which is porous in nature. In this case, the value of the porosity is measured as a percentage. However, the true porosity includes the volume of the pores that are sealed. 7. How can we do quality control of the density log? Explain. Clean formation is usually more than shales. As a result of this the bulk density will read less than the actual density. Therefore, the density porosity which is computed will be higher in terms of shales as compared to the actual porosity. Analysis 1. What logs would you use to identify gas zones? Briefly explain. Neuron porosity logs and density logs are used to identify gas-liquid contacts and detect gas zones. This is because of the excavations effect which makes the logs show low values of porosity. 2. How do SP and GR complement each other? The SP and GR log complement each other in the sense that Sp log uses electrical charge for the purpose of recording whereas the GR uses Gamma rays. Both of these measure different attributes which are existent in the well. 3. When would and wouldn’t you advise to take SP and GR logs? These logs would not be advisable in situations where there is excessive radiation or electrical charge in the well. This is because these may cause fault in the equipment. They are, however, advocated in situations where the quantities of such attributes are average. Exercises 1. Using the suits of logs in the figure below: a. At 10260 ft: (1) Calculate Vshale from SP and GR and briefly explain/compareyour results; (2) What is the porosity?; (3) What can you say about the lithology? Vshale = Igr = (GRlog-GRmin)/(GRmax-GRmin) =(0.45-0.15)/(80-20)=0.005 Vshale = Isp = (SPlog-SPmin)/(SPmax-SPmin)= (0.45-0.15)/(-60-0)= -0.005 The rocks in the environment under survey are those that have minimal porosity. This is attributed to the fact that they can withstand the temperature at such altitudes without weathering. The lithology in this case is of a metamorphic nature. b. Identify the zone(s) with relative low permeability. Briefly explain. The zones with relatively low permeability are those that are above 10400ft. this is because of the low temperatures in these regions. c. Identify the zones with potential gas. Briefly explain. Gas is found in regions below 10000 ft. This is because above this, the temperatures are more encouraging for liquids. 2. Using the suits of logs in the figure below: a. Calculate porosity from the sonic log at 11620 ft and compare it with the corresponding SPHI curve value. What can you infer from your result? =10/25 = 0.4. This shows a greater degree of porosity in the soil. b. Do you expect high content of clay/shale in this logged section? Briefly explain. There will be no much clay in the section. This is because the porosity is generally high. c. What can you say about the quality of the caliper in this logged section? Note: Assume that the logged section has only water, and it belongs to a carbonate formation. The quality of caliper in this section will be low. This is because the porosity will take away a significant amount of materials from the region. The result of this is reduced quality of rock and soil. Work Cited Gunter, Faure. (1998). Principles and applications of geochemistry : a comprehensive textbook for geology students. Upper Saddle River, NJ: Prentice-Hall. Read More