Modelling of Casing Reciprocation During Cement Displacement in ERD Wells

Abstract

Ensuring a quality cement job when cementing long sections of casing in high angle, extended reach wells is both critical and challenging due to the high risk of channeling and pressure related issues. Casing reciprocation is intended to mitigate against channeling; however, this technique is not widely used in ERD wells in the industry. This paper presents modeling, operational observations, and the results of 10¾-in production casing reciprocation during cement displacement on several extended-reach drilling (ERD) well projects. Accurate estimation of hydraulic lift force is one of the major challenges when planning casing reciprocation during cement displacement. The severity of the hydraulic lift force can cause the complete loss of slack-off weight when reciprocating on the down stroke, which is often perceived as the casing being "set" off-bottom. In order to accurately predict the hydraulic lift force and the associated hookload fluctuations, advanced modeling combining torque, drag, and hydraulics was developed. The model takes into account all of the key parameters such as slurries density and rheology, displacement rates, casing stroking speed, wellbore geometry, temperature and pressure effects, etc. In excess of 10 casing reciprocation jobs during cement displacement have been successfully modeled and executed to date. The first several wells were used for model calibration, and the modeled loads for the remaining wells showed consistent and accurate predictions when compared with the measured loads during the cement displacement. The casing strings that were modeled and subsequently reciprocated during cement displacement varied in setting depths from 2000 to 3100 m MD, with the top of cement lifted to the previous casing shoe. It was observed that the effective hookload when stroking the casing down can significantly decrease when the hydraulic lift force is high due to the combined action of surge and circulating pressure. Slack-off hookloads were monitored in real time to determine cementing friction factors. The friction factor data allowed for calibrating the model, which gave confidence to continue reciprocating throughout the entire displacement until bumping the plug. The casing reciprocation campaign has contributed to an increase in the quality of the cement bond throughout the casing string, thereby no longer requiring any remedial cement jobs, which was a common requirement on the previous wells. The technique and observations presented in this paper help close the gap that exists in the industry concerning the effect hydraulic lift force has on casing reciprocation operations. Understanding the effect is important in ERD wells, but can also be useful on other types of wells.

Cementing Process in the Presence of Fluid Loss

“…On the other hand, during cementing jobs this rotation movement is not usual. In some special cases, minor rotations coupled with vibrations, or even reciprocating (up and down) movements, may be applied to the inner casing to assure an uniform mud displacement ( [22,124]). But, during the slurry setting time, the objective is to fix the casing permanently in place, and so flow azimuthal velocities can be neglected.…”