Research On Resistivity Logging Through Steel Casing

Through steel casing formation resistivity survey logging is a new technology developed overseas in recent years that can ensure the saturation of remained oil in the formation, may survey outside the stell pipe of the well resistivity, its survey depth is deeper thatn R/O logging and the neutron lifetime logging,may in the low porosity, under the low permeability formation condition the normal work, may with the bare hole electrical resistivity logging curve contrast, fast qualitative judge the oil layer directly the use degree, has made up the radioactivity logging technology insufficiency. Might discover in the past as a result of the oil well logging engineering factor limit, but had not discovered oil layer, might also appraise the oil layer flooding degree, the monitor reservoir fluid degree of saturation change, further adjusted for the oil-field development plan provides the basis. Therefore this instrument's development has the important meaning.Crosses the metal case well to measure that the formation resistivity is surveys the formation resistivity in the metal case well, its oil well logging principle is similar in the bare-hole the laterolog principle, but its survey difficulty is higher than by far in the bare hole surveys the formation resistivity the difficulty. This article according to the drive pipe formation resistivity oil well logging basic principle and the measuring technique, studies the strong conductive bore hole electric field distribution, regards as the entire bore hole is the strong conductive medium, by this analysis bore hole in as well as periphery in the stratum electric field distributed situation, then the analysis proposes in the steel bushing tube well the electric field distributed situation. Has analyzed the metal sleeve survey formation resistivity oil well logging principle, the method as well as the influencing factor. This article to the metal sleeve electrical resistivity logging's rationale, the numerical calculus result as well as each kind of influencing factor including the well cementation cement, the sheathing material, end the wrap pipe junction band, the drive pipe and other had the possibility the formation resistivity to have the influence to the measuring tube outside the factor to carry on the exhaustive analysis, based on this using the improvement transmission line equation law, studied the drive pipe electrical resistivity logging simulation response, the weak signal detection magnitude, the analysis had introduced the environmental factor to tested the result the influence.Has studied the metal sleeve survey electronic resistivity meter's instrument structure exhaustively, the electronic circuit design as well as the key technologies realizes the method, through provides the theory basis to the electric field distributed situation's research for the case well electrical resistivity logging frequency's choice, may lay the foundation for the later instrument's development. The electric instrument for logging oil electrode array and working's deep research causes the case well formation resistivity logging instrument to the case well to develop possibly becomes successfully.Usually wants the drive pipe to carry on to the formation resistivity survey must to the drive pipe for by the big electric current (8-10 peaceful), surveys the stratum dropout electric current the size, thus definite formation resistivity. As a result of drive pipe's existence, moreover the stratum electronic resistivity must be greatly more than drive pipe's electronic resistivity, causes to measure that the wanted signal turns is weak, even achieves accepts Fu Ji the voltage signal. This proposed to a/D switch the high accuracy transforms the request, has selected∑a△24 A/D switch according to the demand, its resolution may achieve accepts bends down the level, can guarantee that to accepts bends down the level voltage signal collection, through has studied the weak signal high accuracy data acquisition technology, realized the sensor to signal gathering, the signal to enlarge, A/D to transform, the code, the actuation. Examines in the test equipment to accept successfully bends down the level signal, obtains outside the drive pipe to experiment medium the electronic resistivity. After a sensor gathering electrode system's electric potential, two voltages, two electric current parameters pass through the above several steps, forms the graceful code to deliver to the ground carries on processing. In is developing the simulation in the foundation, used the oil field real drive pipe to construct a set of drive pipe electrical resistivity logging weak signal detection test equipment, and has carried on the massive laboratory experiment. Through gives the high and low current electrode on the drive pipe to use the high efficiency alternating current supply (frequency is alternately 0.1Hz, power line voltage 200V, supply current 8A) supplies power, the measuring instrument through the simulation cable connection checking device, the change different external connection resistance's resistance number, might carry on the test to the instrument, and confirms the result.In summary, this article main contribution and established the one whole set to carry on the formation resistivity survey about the steel thimble the theory, based on this and unified the actual situation to do the massive laboratory experiment to confirm each computing technique the feasibility, has had to the drive pipe electrical resistivity logging instrument's development profits from the significance. Therefore, may say that this article the research not only has the theory value, has the use value.