| 摘要 |
1344194 Borehole logging SCHLUMBERGER INLAND SERVICES Inc 19 April 1971 [2 Feb 1970] 20713/71 Heading G1N The invention relates to the processing of borehole logging data. Logs are made with standard "logging tools" of:- Deep and Shallow Resistivity, (which is dependent mainly on distribution of fluids in the formation pores). Spontaneous Potential (which is different in shale and sand). Gamma Ray Transmission (dependent on electron density which is proportional to bulk density of adjacent layers). Neutron Log (representative of hydrogen in water or oil in pores, i.e. porosity of layer). Sonic Travel Time (dependent on nature and porosity of rock). Data from a number of runs may be recorded and combined on a single tape. Interpretation of the logs is firstly dependent on the fact that gamma-ray and neutron logs are not affected by shale whereas the other logs are affected. This is illustrated in Fig. 11, by a cross-plot of density-derived porosity # D versus neutron-derived porosity # N , the effect on a plotted point of various types of shale relative to the "clean-sand-line" is indicated. The shale line represents substantially zero porosity but includes a certain amount of water associated with the clay. The effect on the plot of the proportion of shale V sh and the porosity # D can be represented by lines parallel to the sand and shale lines respectively Fig. 3 (not shown). Thus if the volume of shale is determined from other logs, the plotted point can be shifted parallel to the shale line by this amount e. g. as illustrated in Fig.15 (not shown), and if the point then lies above the clean sand line the presence of hydrocarbons may be indicated. The shale indicator is then re-checked and cross-checked several times, with parameters computed from the other logs. Equations for mathematically performing the above technique (together with corrections to be applied to the logging data and cross-checking parameters). The calculated values of V sh are arranged so that they will be equal to or greater than the true V sh , thus the nearest-correct value will always be the smallest computed value. Flow diagrams are given Figs. 19A..24B (not shown) for preparing programs to carry out the above analysis in a digital computer. These diagrams list the equations according to reference numbers in the description and indicate when checks are to be made in "decision elements" and the data discarded or recycled and corrected. A final stage prepares data for print out. |
