Rig Site Tips: Inner String Cementing Procedures and Instructions

Protecting the surface formations is very important to avoid facing any problems when drilling ahead to reservoir. The surface casing is cemented following a special procedure. It is cemented using the stinger which is made up on drill pipe and run to the surface casing shoe. The success of the operation is related to many points which have to be guaranteed before, during and after performing the cementing job.

Before the cementing job, the casing has to be checked, cleaned, measured and drifted. The casing tally has to be prepared (Click Here for General Running Procedure). The setting depth has to be discussed with well site geologist to give the window where the casing shoe should be set. The casing running equipment should be on site, also the cementing crew, unit and products should be on site. The jet cellar or electrical pump should deliver a pumping rate equals or more than the expected cementing flow rate. It has to be checked and tested before starting drilling the surface section. 

Once the setting depth is reached, the well should be prepared to run surface casing. The drilling mud should be conditioned. The driller has to get instructions to work on any tight spot faced when pulling out of the hole (Click Here for Tripping Instructions). When the drill bit is on surface, it should be cleaned and dull graded, then the rig floor should be prepared to rig up casing running equipment. 

Prior to run the first joint of casing, the bell nipple should be removed and the top of the conductor pipe should be cut to cellar ground level (this is an option, you can keep it as it is and cut it after finishing the cementing job). Once these preparations are established, the crew proceed to run the surface casing to the shoe setting depth. The landing joint should not screwed with the full required make up torque to make it easy to remove it.

Fig 01 - Surface Casing Before and After Removing the Landing Joint

When getting the shoe at the setting depth (at least the last two joints should be run with circulation to avoid plugging the casing shoe) the IPN beams should be prepared with a second side door elevator. The coupling of the last join should be landed on the IPN beams and side door elevator and centralized into the conductor pipe using chains, then the welder proceed to weld three bars of steel around the surface casing and anchor it at the conductor pipe in triangle form. After anchoring the surface casing string, the landing joint can be removed smoothly in order to avoid decentralize the surface casing, then rig down the casing running equipment.

Fig 02- IPN 

 In order to make sure that the stinger do the job properly, the sealing adapter and thread should be checked, also the stinger has to be tested into the stab-in shoe. Make up and run in the hole with centralized stinger, pup joints should be prepared to use them when spacing out. Establish circulation above stab-in shoe, then Stab into the shoe and slack-off. Establish circulation for 120 % of the drill pipe string volume. Check and make sure that there is no flow between the drill pipe string and the surface casing. The mud should flow between the conductor pipe and the surface casing. If no losses are recorded and the mud is flowing normally between the surface casing and the conductor pipe, the crew line up and switch to the cementing unit and pump volumes as cementing programs. While pumping lead cement and get it at the surface, the cement crew proceed to pump the tail cement without waiting to finish the total lead volume because it can be overestimated due to the level of excess factor used in calculations.

Fig 03- Stinger 

When getting cement at the surface, it is better to use a hose of water in the cellar to dilute the cement and make it easy to the jet cellar and the electric pump to work effectively. 

When the total volume of cement is pumped, pick up and un-stab the stinger and watch for any back flow. If any back flow is noticed stab-in and hold for fifteen minutes or more according to the cement surface sampling, then un-stab again, no back flow should be noticed due the cement gelling process (Click Here for Cement Properties). Pull out one joint drill pipe and circulate with fresh water to clean the inner drill pipe string from cement, then start to pull out the stinger to surface. 

Once stinger is at surface, proceed to remove the IPN beams and side door elevator then cut and bevel the surface casing in order to install the casing head housing and nipple up the blow out preventer (BOP). 

Fig 04- Casing Head Housing

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