In 1989 short-radius lateral drilling technology was applied in the Khafji Field which is situated in the Divided Neutral Zone between Saudi Arabia and Kuwait.

First two lateral holes, with a combined horizontal displacement of 1389 ft, were drilled in a limestone which has two porous oil-bearing layers separated by a tight limestone, starting from one existing vertical production well. The aim in so doing was to enhance the rate of oil production.

A third lateral hole, with a horizontal displacement of 309 ft, was drilled in an unconsolidated oil-bearing sand formation which is characterised by bands of sloughing shale, starting from another existing vertical production well which was suffering water coning. From the standpoint of wellbore stability this sand formation had been considered to be too unstable to carry out horizontal drilling. The aim in view here was also to enhance the rate of oil production. However, the main intention was to prevent the problem of water coning.

Lateral drilling in the limestone was completed without any difficulty.

Inclination was able to be controlled by changing the bottom hole assembly. Drilling was carried out-until the allowable maximum rotary torque was reached.

However, during lateral drilling in the. sand formation many problems occurred – i.e. low rate of penetration, short bit life, severe dragging during trips, differentially stuck, etc. These problems were due to the high mud weight which was considered to be necessary as a result of an analysis, taken together, of a microfrac test and a rock mechanics study which had been carried out. The aim here was to stop the hole collapsing. In this case inclination was not controllable. The well path kept on rising continuously.

This paper will discuss how the well was drilled, the problems encountered in the process and how these were overcome.

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