An Innovative One-Trip Optimized Wellbore Solution for Non-Cemented Liner, Wellbore Cleanup, and Sand Screen Placement Completion

Abstract

An innovative optimized wellbore solution has been developed to change how the industry completes lower or intermediate completion installations. In an openhole, non-cemented liner and sand screen type of completion, traditionally two trips are required. The production packer area is cleaned, the wellbore fluid is filtered, and fluids are displaced in the first trip. In the second trip, the sand screen with liner hanger will be deployed. Sometimes a third trip is run with a retrievable packer to perform negative liner top inflow test.

This optimized wellbore solution allows for setting the lower completion, cleaning the wellbore, and enabling displacement from drilling fluid to completion fluid in the wellbore in a single trip. On wells where there are concerns over equivalent circulating densities, the optimized wellbore solution would include tools to isolate tubing pressures to the formation. This method would use the wellbore test packer (inflow test packer) and drillpipe shut-in valve while conducting the upper clean up and fluid displacement. It significantly reduces operating cost without impacting operating efficiencies.

A number of wells have been completed by this system. One completion was conducted for a major operator west of Shetland. An integral wellbore clean up string, along with the liner hanger and sand screen, were successfully deployed and helped the operator achieve their commercial goal of reducing operating cost. The saving was a reduction of approximately 32 hours. In this paper, the one-trip optimized wellbore solution will be presented, along with the case history west of Shetland.

Introduction

A service company investigated innovations that could help the industry cut completion costs by reducing the number of trips required to clean and complete a well. Fewer trips would save money by lowering rig time. The operator would also benefit financially because the well could enter production sooner. Standard industry practise for delivering a clean wellbore and landing a lower completion required a minimum of two trips, while the majority take three trips to deliver the wellbore to an acceptable upper completion. The challenge for the service company was to look at the portfolio of all their product lines to see what changes could be achieved to reduce trip times and costs. By applying advanced technology and expertise in completion service, a decision was made to challenge existing best practises and deliver a new optimized wellbore solution. The service company engineers and a major operator in the North Sea developed this new system in partnership, and the first integrated operation of this type was executed flawlessly in the operator's well.

Case Study

A producer well offshore west of Shetland was drilled and completed with 9 5/8 in. casing to 2,493 m total depth (TD) and 8 1/2 in. open hole to 4,035 m TD. The water depth is 140 m. The reservoir temperature is roughly 171°F at 1,950 m TD. The lower completion consisted of 5 1/2 in. liner/screen to TD, with a combination of swell packers and sandface valves. The upper completion consisted of a production packer and gas lift mandrel.

The objectives of the completion were to

l Run both completions safely

l Perform full pressure integrity and functionally tests of the liner hanger

l Conduct a high quality cleanup of the casing, wellhead, blowout preventers (BOPs), riser and surface lines prior to running the upper completion.

l Complete the well with minimum nonproductive time (NPT) and cost

The 5 1/2 in. liner and 9 5/8 in. casing needed to be displaced from 1.11 specific gravity (SG) oil-based mud (OBM) to brine via a seawater interface and viscous surfactant pills. The additional requirements for the displacement operation included no discharge of waste fluids released to the environment. Also, clean up was to be completed on the first attempt with no contamination of clean fluids on surface. Standard industry practice for delivering a clean wellbore and landing a lower completion required a minimum of two trips. while the majority of operations took three trips to deliver the wellbore to an acceptable upper completion. Typically, the production packer area is cleaned, the wellbore fluid is filtered, and fluids are displaced in the first trip. In the second trip, the sand screen with liner hanger will be deployed. Sometimes a third trip is run with a retrievable packer to perform negative liner top inflow test. With support from the operator, the service company recombined several advanced technologies to yield an optimized wellbore solution. The new system completes all above operations in one trip, saving operating cost without impacting operating efficiencies.

The one-trip wellbore cleanup and liner hanger bottom hole assembly (BHA) is shown in Fig. 1. While run in hole (RIH), the wellbore tools acted purely as a conduit for deploying the liner hanger. At the required depth, the liner hanger was deployed and the setting tool was released from the liner hanger. The integrity tests were performed. Fluids were then circulated and displaced with sea water. The J-type circulation valve was activated to boost the annular velocity and facilitate circulation above the liner top. The production packer area was then cleaned by the non-rotational casing scraper. The nonrotational feature minimized any damage to the casing inside diameter (ID). When pulled out of the hole, the magnets collected metal debris and the Multi-task Wellbore Filter cleaned the downhole fluid and brought the solids to the surface. The detailed running procedure used is listed below:

1. After drilling TD is reached, conduct planned reservoir circulations, fluid displacement/conditioning and back reaming

2. Conduct dry trip to TD to simulate running liner

3. Conduct casing circulations, pull out of hole

4. Flush BOP/riser with drilling assembly and test BOP

5. Makeup and run in hole with lower completion, complete with deep wellbore cleanup tools

6. Set lower completion liner hanger and release running tool

7. Wait on lower completion isolation valve to close

8. Pressure test lower completion isolation valve to 4,000 psi over 1.11 SG

9. Pickup running tool, closing isolation valve

10. Pressure test lower completion to equivalent of 4,000 psi over 1.11 SG brine

11. Displace liner to seawater via 2 7/8 in. wash string

12. Set down weight onto liner top to open J-type circulating swivel, complete high rate displacement of 9 5/8 in. casing to seawater

13. Displace well completely to 1.11 SG brine

14. Pull out of hole scraping 9 5/8 in. production packer setting depth and annular safety valve setting depth

15. Recover wear bushin

16. Conduct final riser cleanup and BOP jetting

After applying the above system design, the liner is set, the screen and fluid loss system were deployed, the fluids were displaced successfully, and the wellbore was cleaned up. All these operations were completed in one trip. 32 hours of rig time were saved. That contributed to a new delivery-time record for the operator, surpassing the previous one by four days. This operation exceeded the operator's requirements.

Case Histories:To date, eight optimized wellbore solutions have been deployed and completed on platform wells in the North Sea. These systems included a combined slotted liner with a UniflexTM liner hanger system and wellbore cleanup tools. All work was completed as planned with positive feedback received for each job.The benefits included more than reducing trips into the wellbore. Use of multi-disciplined field supervisors resulted in reducing persons onboard by 50%.Additional optimized wellbore solutions have been planned for 2011 as a result of the successful run history and significant cost saving to the operators.

SummaryThe first integrated lower completion/wellbore clean-up trip, on a semi-submersible, was recently conducted in the North Sea by a service company offshore west of Shetland. This innovative solution was designed to help the operator reduce operating costs by providing an integrated, one-trip system. By incorporating a special design that enabled the lower completion and deep wellbore cleanup to be combined, 32 hours of rig time were saved. That contributed to a new delivery-time record for the operator, surpassing the previous one by four days.