Enviroment Correction Of The Logging Curves Under The Unbalanced Condition

At present, underbalanced drilling system has been applied in the drilling engineering to protect hydrocarbon zone. The slurry used in this system includes Formate solid-free, micro bubbles, inflation and purified-Nitrogen slurry. They have low density which makes the press in the slurry slight over or almost the same as the press in the bottom of the well.In this paper, calibrated model for logging curves was builded by Litho-electric experiment, multi-dimension-grid technology and correction charts . Considering the physical truth of Tuha oil field and applying the histogram mathematics statistics technology, the logging suites and processes were designed fit for the underbalanced drilling system. Finally, the purposes were achieved for safe well logging, correct data access and accurate recognition of oil-gas-water. The main achievements obtained were as follows, 1.Formate-mud had more influence on resistivity, natural gamma and density than sound wave and neutron. 2. Micobubbles had large effect on the neutron but little effect on resistivity, sound wave, natural gamma and density. 3.Unlike resistivity, sound wave, and density, inflation slurry had bigger influence on neutron and natural gamma. 4.nitrogen drilling common-mud well-logging environment had no influence on the resistivity, sound wave, density, and natural gamma well-logging. Lateral resistivity logging had to be replace by induction logging and array induction logging,because it could not word due to oil-base cement slurry. Such conditions had larger influence on the natural gamma and the physical conditions of the stratum could be indicated by array induced, sonic logging, neutron logging and density logging. 5.By simulating Formation Invasion experiment, the calibration relationship was obtained between deep-lateral resistivity and porosity, stratum water and slurry resistivity.