Liner Hanger Installation in Challenging Offshore Well Conditions
Authors: Luna David , Elizalde Roberto , Diwaku Wantuadi 
Published: February 2017

ERD wells are commonly associated with major challenges for installation of casing and liner strings. These wells typically present high torque and drag parameters that jeopardize getting strings to total depth.

In an attempt to optimize production, a major oil company in Angola decided to re-enter the study well in early 2016. A sidetrack was opened in the 9 5/8-in. casing, and drilling continued in the 8 ½-in. hole and penetrated the target zone in the highest location. Then a 7-in. production liner was run.

To reach the target zone, 5,583 ft of 8 ½-in. hole was drilled and deviations varied from 45° to 87°. This trajectory was a challenge for subsequent running of 7-in. liner. Torque and drag (T&D) models showed liner rotation at total depth (TD) was not possible, and a surge model indicated likelihood of mud losses while running the liner.

Liner hanger technologies became a very important phase of well construction, and service companies developed advanced liner hangers to overcome hostile well environments. In this case study, the short time available from the planning to execution phases and the current oil market conditions made it imperative that the right equipment, service, and technology were available in country. To achieve the ideal working parameters and get the liner to bottom, a thorough assessment needed to be performed to ensure risk mitigation.

This paper presents summarizes steps considered during planning for the 7-in. liner run including a detailed engineering analysis that enabled the operator to make the best decisions based on the available resources. The paper will also discuss lessons learned and best practices captured during the job that will be used for subsequent liners in similar wells.

The case study well was planned as a sidetrack from an existing well that had been shut in because of low performance. The main well had been drilled and completed as a single gravel pack in 2007. The objective of the sidetrack was to penetrate the reservoir organized complex in the structurally highest location to access reserves and optimize production. A constrained initial production was estimated at 6035 BFPD.

An operations overview of the complete intervention is as follows: Set a 8 ½-in. whipstock in existing 9 5/8-in. casing at 8,400 ft and mill the window.Drill an 8 ½-in. hole section to 13,923 ft MD / 6,657 ft TVD.Run and cement 7-in. liner.Displace the hole with completion fluid.Perform cement bond logs and hand the well over to completion.

The 8 ½-in. hole was drilled as shown in Fig. 1 and Table 1. The well trajectory offered a challenge to get the 7-in. liner to bottom and to achieve a good cement bond in the production section. Figure 1Well trajectory for case-study wellTable 1Geometric features of case-study wellMeasured depth at whipstock point8,400 ftTVD at whipstock point5,279 ftDeviation at whipstock point78.25°Length of 8 ½-in. hole5,583 ftMeasured depth at TD of 8 ½-in. hole13,983 ftTVD at 8 ½-in. hole TD6,695 ftMaximum deviation in 8 ½-in. open hole86.9°Maximum dogleg severity in 8 ½-in. open hole5.21°/100 ft at 8,933 ft MD

The operator and the liner hanger service company used proprietary simulation tools during the planning phase to predict possible issues for running the liner. The simulation considered main aspects, such as well trajectory and the influence of the whipstock installed in the 9 5/8-in. casing. All analyses were performed and maximum working parameters were defined and included in the well program. The operator also considered possible limitations that using standard equipment available in country might impose on well life. The final management decision was to proceed with the plan presented.