Pump and pull cementing method is introduced to overcome soft cement plugs due to the swabbing effect and contamination in an oil-based mud environment. The method aims to address quality concerns in challenging well profiles where conventional cementing techniques are deemed to fail, which potentially lead to additional cost for remedial cementing work and non-productive rig time.
The method is utilized to tackle a re-occurring issue of tagging soft cement plugs that are used for several applications, including plugging and abandonment and sidetracking operations, in deep highly deviated or horizontal wells. In such profiles, fluids and cement don't balance themselves as gravity is not the predominant factor. Subsequently, the cement plug cannot be balanced, and contamination takes place resulting in its failure. The method targets minimizing this by reducing the effect of pulling out of the plug by keeping the drill pipe stinger inside the cement slurry and replacing the volume created while pulling out of the hole by pumping cement until completing the placement of the plug.
The technique is time sensitive since most of the cement slurry remains in drillpipe while preforming the job. For that reason, intensive planning is required to ensure successful implementation. One factor that impact the quality of the job is the abundance of actual downhole data, including caliper and temperature logs. Based on that, cement slurry design can be adjusted to account for temperature effect as well as adjusting volume calculations. Also, lab and computer simulations play a significant role in determining several parameters such as spacer formulation, mud removal efficiency, ultimate compressive strength chart, and additives concentrations, especially retarders. In terms of field preparedness, specific equipment and competencies are required for such critical jobs. The method was deployed successfully in several jobs, resulting in excellent cement quality. At the top of that, the method was used to optimize operations by pumping a single long cement plug instead of several balanced cement plugs. This has directly resulted in saving several rig days while delivering satisfactory cement hardness. A couple of case studies are introduced to showcase the effectiveness of the method in challenging applications.
Pump and pull technique proved that it resolves the challenge of placing cement plugs in highly deviated and horizontal wells. It earns more importance as wells are growing in complexity. Recently, the technique was used to successfully place significantly longer cement plugs, achieving an outstanding level of operational efficiency by saving rig days and resulting in cost optimization of cementing operations by reducing the number of required plugs to be pumped.