Authors A. Puliti (eni) | A. Maliardi (eni) | G. De Grandis (eni) | C. Molaschi (eni) | F. Arpini (Ava / Newpark Drilling Fluids) | L. Bussaglia (Ava / Newpark Drilling Fluids) | F. Paoli (Schlumberger) | F. Zauli (Schlumberger)
Document ID SPE-177545-MS
Publisher Society of Petroleum Engineers
Source Abu Dhabi International Petroleum Exhibition and Conference, 9-12 November, Abu Dhabi, UAE
Publication Date 2015


This paper describes the successful drilling of a complex 3D High Dog Leg Severity (DLS) well trajectory with extended horizontal section, achieved thanks to the combined use of an innovative Rotary Steerable System (RSS) and a new type of High Performance Water-Based Mud (HPWBM).

The well under discussion is a 6 in. side-track of an existing wellbore, drilled to optimize production in a field characterized by a carbonate reservoir. The challenge has been to reach the target and land the well in the shallowest part of the reservoir, far away from the Oil Water Contact (OWC). Furthermore, high Rate Of Penetration (ROP), smooth borehole, real time logs and good hole cleaning had to be provided to ensure optimum drilling performance while reducing the risk of wellbore stability issues.

In the past, in this field, development wells have been generally drilled with a 2D trajectory design. In addition, standard drilling fluid practices have been using low weight calcium carbonate polymer muds to drill through the reservoir. Although generally successful, this resulted in high torque and low ROP in wells with extended horizontal sections.

In the case history described in this paper, the side-track well trajectory has been planned with a DLS developed in three dimensional planes. An innovative hybrid RSS, specifically developed for high DLS applications, has been selected to drill the curve section. Moreover, a novel HPWBM has been introduced to drill the curve and the horizontal section. The use of the New Generation HPWBM has further optimized drilling performance, showing excellent results in reducing torque and increasing ROP, allowing to extend the horizontal section and maintain wellbore stability.

The combined application of the innovative RSS and New Generation HPWBM has led to an improved control of the trajectory, reducing the well path tortuosity, and has greatly enhanced drilling performance compared to offset wells in the field. The curve section has been drilled with a DLS up to 10°/30 m and landed with a 90° inclination. Then, the side-track has reached the target with an extended lateral drain of 2010 m. In previous similar experiences, high torque values determined the maximum length of lateral drains.

An average ROP of 3.8 m/h has been achieved while drilling the curve while an average 7.5 m/h ROP has been registered in the horizontal section.

The outstanding results have opened up the way to further applications with similar challenging targets and high DLS requirements.