Well Head Replacement

Step by step documentation and guidelines for Thums/Pier J wellhead

removal and replacement.By: Johnathan Cunningham

Wellhead Removal•Performed casing cut approximately 10-15’ below wellhead.•Engage casing spear in casing. •Open load indicator on blocks•Have welder cut 13 3/8” surface casing•Pick up on wellhead with casing spear to make sure the wellhead is free (ensure that pack off rams are run in prior to picking up on wellhead). •Set wellhead back down and disengage casing spear•Wrap a braided sling (NOT a pipe sling) around wellhead and pull out of the cellar with the blocks (use block shackle).•Remove wellhead and tail out with forkliftNote: RBP was in the hole as well as kill fluid below the RBP providing two forms of well control prior to performing wellhead removal.

13 3/8” preparation for repair•Once wellhead is removed assess the condition of the 13 3/8” (in some instances cellar demolition is needed in order to expose good casing to weld onto like in the photo to the right).•Have a UT scan performed on the 13 3/8” to verify where good wall thickness exists for the new J nipple.•It is preferable to have 50% wall thickness to weld onto to make the necessary repairs.

Note: Cellar floor base is approximately 2 ft in thickness on Thums and Pier J.

Dressing 13 3/8” for welding•Cut and remove both the 20” conductor pipe and the 13 3/8” to the desired height.Note: Be sure to prevent any concrete or other foreign material from falling into the wellbore by removing ANY loose debris from around the wellbore. Once the prep has been completed place a cover over the wellbore.

J nipple and well head installation•Once the 13 3/8” has been prepped welder can begin installing the new replacement j nipple.

Note: Be sure to utilize a 13 3/8” collar on the pin end of the replacement j nipple and thread on as far as possible (see green collar in photo). This helps the j nipple retain is roundness when exposed to heat cycling during the welding process.

•Once the j nipple has been welded in place secure make up flange (shown in yellow in the photo) to the wellhead.

•When making up wellhead ALWAYS rotate to the left until you feel/hear the wellhead “jump”. This helps to ensure that the wellhead is started on its threads properly. If the integrity of the j nipple is intact through the welding process the wellhead should thread on with only a few threads still showing.

Note: If the wellhead will not rotate by hand beyond a few revolutions back off the wellhead and attempt to start threads again.

•Make up wellhead with casing tongs to between 2400-2700#.

•Note: It is easiest to orientate the wellhead by running a stick through the casing valves. This offers a more accurate reference point for wellhead alignment.

Setting Casing BowlOnce all remedial work has been performed on the casing (recovering casing, dressing casing stub and running on casing bowl with replacement casing) It is time to set the casing bowl.

•The casing bowl “swallows” approximately 3 ft of the preexisting casing. This is achieved by picking up on the casing 50-60k and dropping it rapidly, allowing the casing bowl to be worked down onto the stub.

Note: Sometimes rotation is needed in order to work the casing bowl onto the casing stub. There is a lip guide on the casing bowl that helps to align the bowl with the stub.

•Once the casing bowl has bottomed out on the stub it is necessary to test the bite achieved by the bowl. This is done by pulling at increasing weight increments (60k, 80k, 100k). If the bowl is successfully installed the weight pulled will not bleed off.

Note: Please ensure all personnel are off the work floor during this testing phase.

Rough Cut CasingOnce the casing bowl has been successfully installed it is time to remove the BOP assembly. This will expose the casing that is sticking up out of the wellhead. At this time we can prep the casing for the emergency slips and pack off assembly.

•Have the welder rough cut the casing to approximately 1 ft above the wellhead. This will allow for the install of the emergency slips assembly.•Remove any burrs and slag from this cut to allow for the emergency slip installation.

Emergency slip installationThe emergency slips are what hold the casing in tension. They are usually set at around 70-80k. This is why it is important to test the casing bowl in the previous step to 100k to ensure that the bowl is set properly.

Note: Break the retaining Allen bolts loose (4 carbon steel bolts) on the e slips prior to dropping them over the casing stub. This will make it easier to remove them while the slips are inside the wellhead.

•Slide the emergency slips over the casing stub. Once the stub has cleared the wellhead remove the retaining Allen bolts so the slips can drop down to engage the casing.

Note: It may be necessary to hammer the emergency slips downward to get them located properly inside the wellbore.

Emergency slip InstallationOnce the emergency slips are in place pick up the casing spear and engage the casing.•Pull between 70-80k with the casing spear and slowly return the casing to neutral weight. Repeating this several times helps work the emergency slips down into the wellhead.•Once the slips are set remove the casing spear from the casing stub.

Continue cutting casingPerform another rough cut inside the wellhead to provide more room for the final cut and dressing of the casing stub.

•Be sure to leave at least 3 ½” of casing above the emergency slips.

Dressing casing stubIt is now time for the final preperation of the casing stub for pack off installation

•Bevel the casing stub in a “V” shape.

•The high side of the bevel should be located on the inside edge.

•Be sure that any burrs or rough edges are ground down smoothly to prevent damage to the O rings located inside the emergency pack off.

Casing stub final dress and measurementsThe final measurement on the dressed casing stub sticking up from the emergency slips should be no more than 3 ¼” and no less than 3”.

•Ideally you want the stub to measure 3 1/8” .

Note: Be sure to make several measurements around the entire perimeter of the casing stub to ensure that the proper height has been achieved.

Pack off installationAfter the casing stub has been sized and dressed it is now time to install the pack off.

•Slide pack off assembly inside of the wellhead and set it on top of the casing stub.

•Utilize a piece of 4x4 and a sledge hammer to start the pack off onto the casing stub

•Note:Grease the inside of the wellhead and casing stub to reduce the chance of binding while installing the pack off.

•Once the pack off is started over the stub use the pack off puller and the weight of the blocks to “hammer” the pack off onto the casing stub. In the photo to the right you can see how the pack off puller top edge is in alignment with the wellhead. This is a good indicator that the pack off is fully landed onto the casing stub.

•Note: Be sure to have the 13 3/8” valve(s) on the wellhead open to alleviate any pressure generated by the force applied to the pack off during installation.

Pack off installationOnce the pack off is seated remove the pack off puller and inspect the depth the pack off is bottomed out at.

•If the pack off is seated BELOW the casing rams (see photo) the installation is complete.•Run in the pack off rams and packings to ensure that the proper clearance has been achieved.•Remove the plug from the pack off test port and pressure test to 2500#. If the installation was successful the wellhead replacement installation is complete.Note:If you do not achieve a good test and oil is seen seeping around the casing stub or emergency pack off removal of the pack off for inspection is necessary to inspect the o rings located inside the pack off assembly.