The Research On Work-over Technical By Side-tracking Of Casing Damaged Wells

There are 6860 casing damaged wells in Daqing oil field up to 1999, which occupies 16.36% of all the producing wells. In 1999, 700 casing damaged wells were found. With the development of the oilfield, the damaging degree of casing damaged wells became more and more serious, which also enhanced the work-over difficulty. One reason is the diameter of damaged position is small, the other is the proportion of the casing damaged wells which has multi-damaged points are higher. This kind of wells couldn't be repaired with present technical, or the repair costs are too high so they should be abandoned. But indeed the reservoir underground also has developing value. By side-tracking technical, we can use original well site, needn't to land lease and relay ground pipeline, also a segment of original wellbore can be used and no new well needed. So the repair speed expedites, ensures the stabilization of productivity. At the same time it can supply new work-over technical for oilfield which can server for oilfield all over the world.This paper mainly studied the contents as follows:1. Optimizing casing retrieving depth and side-tracking point by minimum cost method due to different kinds of abandoned wells.2. Optimizing design of well path due to different well pattern demand.3. Study on anticollision computing method of well track due to original well pattern data actually measured.4. Completing control method of well path due to the rock characters and the interaction between bit and formation.5. Study on the software of side-tracking wells. The well cross section design software of side-tracking wells is developed, which can satisfied the demand of side-tracking wells design and construction, it also includes well cross section computing and prediction of well track.A series of work-over technologies by side-tracking for casing damaged wells are established through the research in this paper, it includes: optimizing design on well track, bit type choosing, drilling assembly design, hydraulic parameters design, wellbore measurement equipment, new technology and techniques etc.. It supplies new work-over method for major repair wells in the oilfield. The side-tracking software developed can satisfied the demands of side-tracking well design and construction.From this paper, some conclusions are acquired as follows:1. A whole series of side-tracking technology in accordance with geology characters of Daqing and corresponding equipments are formed as the successful research.2. The well track control theory and anticollision technology solves the control of azimuth under small deviation angle and the collision issues between new wellbore and adjacent well or original well under densely well pattern.3. The study and successful application of whipstock open a new area for suspended side-tracking.4. The study on wall destabilization theory and optimizing workover fluid for side-tracking wells ensure the security construction.5. The application of well cementing technical get the equal index with regeneration well on cement quality.