ABSTRACT
Increasing the formation flow area is one important way to improve the downhole flow conditions. Drilling drainholes by means of conventional drilling technique can already be seen as state of the art. Beside this conception, the lateral drilling, or the "short radius kick-off"-version, has already proved to be feasable, although predicting angle building and controlling inclination and direction was critical. One big step forward was now done by developing the Articulated Drill String (ADS).
Its principle results in a very good control of the well course and will be described in the paper. Depending on the geometrical layout, build-up-rates up to 90 deg./ l0 m are possible. Steering the bit is achieved by means of a special configuration of stabilizers.
Three field tests have already been performed. The first prototype was tested in a quarry. This hole was surveyed with conventional mine surveying equipment. The accuracy of the predetermined well course was found to be very satisfactory. Two other field tests have been performed in a German oilfield. The depth was approx. 1000 m. Angle was build up to 110 deg. followed by a straight hole section of 40 m in order to reach the attic oil in the reservoir. The well was completed with a slotted liner.
Typical procedures of handling the ADS, drilling, surveying and logging as well as casing and cementing are described in the paper.
