Basic Well Logging HOMEWORK 1 Show all your calculations for computational questions and explain your reason(s) for conceptual questions. Name: ----------------------------------- Student ID: ----------------------------------- Question 1: Calculate the shale index (Ish) for the depths and intervals below for the log below (log A). Then, use linear, assuming that the rocks in the well are Tertiary in age (Clavier model), and assuming that the rocks in the well are Mesozoic and older in age (Steiber models) to calculate volume of shale. Also, calculate the volume of shale using the SP method. Compare and discuss the results. Hint: 1- For linear, Clavier and Steiber model you can use Chart 1 in the appendix or the following equations: a. Linear (is the upper limit): Vsh I sh b. Clavier (is for Tertiary clastic): c. Vsh 1.7 3.38 ( I sh 0.7) 2 Steiber (is for Mesozoic and older rocks): Vsh 0.5 I sh 1.5 I sh GR GRMIN GRMAX GRMIN 2- For SP log a linear model is used to estimate V shale: SP SPMIN VSH SPMAX SPMIN where I SH Depth (ft) 5760 5775 5840-5860 6020 6040-6050 Vsh linear Vsh Tertiary Vsh Mesozoic & older Vsh SP Log A Question 2: Based on the log below (log B), estimate Rw for the formation at 98929904 ft. Use Rmf = 1.14 -m at 60F and Tf = 162F @ 9900 ft. Hint: 1- Use Arp's equation to approximate the effect of temperature or use Chart 2 in the appendix T 6.77 Arp's equation for Fahrenheit degree: R2 R1 1 T2 6.77 T 21.5 Arp's equation for Celsius degree: R2 R1 1 T2 21.5 2- Use the following for converting Rmf to Rmfe a. If Rmf at 75 > 0.1 then Rmfe = 0.85 Rmf b. If Rmf at 75 < 0.1 then use Chart 4 in the appendix 3- Use static spontaneous potential log equation for converting potential to resistivity or Chart 3 in the appendix Rmfe Essp K log Rwe where K 61 0.133T if Fahrenheit degree and K 65 0.24T if Celsius degree 4- Use Chart 4 in the appendix for converting Rwe to Rw 9950 Log B Question 3: Use log B and based on SP/GR/Caliper divide the interval 9860-9970 into about 5 zones and fill out the following table. Avoid thin zones which are less than 10 ft. label lithology and boundaries of the logs. 1. For each Zone select three points, the top and two others, for collecting data. The intention is to use these three points to analyze the zone. The first point should be at the top of the zone. 2. Record the depth, GR, Caliper, and SP reading for each point 3. Create a column to compute the temperature at the top of each zone. 4. Create a column to compute the ratio of Hole Size to Bit size for each point. 5. Create a column to compute Gamma Ray Shale Index for each point 6. Create a column to compute Vsh for each point assuming a linear relationship between Vsh and Gamma Ray Shale Index 7. Create a column to compute Vsh using SP log Zone Lithology Depth GR Caliper SP Hole Temp. size/bit size Ish Vsh using GR Vsh using SP A B C D E Question 4: Estimate the GRcorr, if GRlog=100, Hole size= 14 in, mud weight=2.16 g/cc and tool diameter is 1-11/16 in. Tool is centered. Hint: Use Chart 5 in the appendix. Question 5: Refer to well log C and answer following questions. 1. Is the borehole in gauge? 2. Are there any washouts? If so, at what depth(s)? Log C Question 6: Locate the following information from the log heading of log D. Name of the Well: _________________________ Date: _________________________ Permanent Datum: _________________________ Kelly Bushing Elevation: _________________________ Maximum Depth: _________________________ Bit Size: _________________________ Type of Mud: _________________________ Resistivity of the mud: _________________________ Resistivity of the mud filtrate: _________________________ Resistivity of the mud cake: _________________________ Resistivity of the mud @ BHT: _________________________ Log D Question 7: If the Sw=30% and Sxo=65%, what is the hydrocarbon saturation and what is the movable hydrocarbon. Question 8: If a formation has a conductivity of 1,500 mmhos, what is its resistivity? Question 9: It is not possible to determine the exact lithology based on only the resistivity log. But the resistivity log can give us some idea about the rock type. The log below (log E) was run in interbedded sandstone and shale. a. What is the most probably rock type @ 10690-10710 ft? ________________ b. Which is more saline, the mud infiltrate or the formation water? c. Is there oil or gas in the logged interval? d. Identify invasion of the mud filtrate at the following depths using deep and shallow resistivity curves. State whether the invasion is shallow, moderate or severe. a. 10700 ____________ b. 10820 ____________ c. 10900 ____________ 0 -160 GR C SP CMV ILDC 150 0.2 1.95 200 0.45 ILM 40 0.2 MSFL ACAL 6 200 16 0.2 200 10700 10800 10900 Log E RHOC 2.95 CNLLC -0.15 150 DT s/ft 50 Question 10: The resistivity of a water-bearing sand was found to be 0.6 -m. If the formation water resistivity is 0.06 -m, give your best estimate of the formation porosity. Indicate any assumptions which you make in developing your estimate. *** END *** Cl ry tia er ~T r( be St ei as tic at ed so lid ~C r( vi e la C Chart 1 s) R ar e n on Li oc ks ) Appendix: Chart 2 Chart 3 Chart 4 Chart 5