Energy Policy Act of 2005 (Ultra-deepwater and Unconventional Resources Program)
Smart Cementing Materials and Drilling Muds for Real Time Monitoring of Deepwater Wellbore Enhancement
University of Houston
Operating in deepwater to produce oil and gas offers unique challenges in well construction beginning at the seafloor. As deepwater exploration expands around the world, preventing the loss of fluids to the formations and proper well cementing have become critical issues in well construction to ensure wellbore integrity because of varying downhole conditions. Large-bore subsea well head design require competent cement placement to maximize casing support and isolation for drilling operations. As more offset wells are drilled for production of oil and gas, it is critical to ensure minimal disturbance to surrounding facilities by not only preventing lost circulation with drilling mud but also proper cementing of the wells. Lack of mud and cement returns may compromise the casing support and excess cement returns cause problems with flow and control lines. Hence there is a need for minimizing fluid losses by proper placement and monitoring of the drilling mud and cementing operation in real time. Unexpected fluid losses could be addressed real-time by changing the compositions of the drilling mud and/or cement slurry.
A number of fluid loss control technologies have been developed in the past three decades and used with the drilling mud and cementing slurry. These technologies must be revisited with the recent advancements in nanomaterials, coupling agents and surfactant technologies. Calipers can be used to accurately estimate the borehole volumes but are seldom used. Therefore tracers and other methods have been used to provide estimates of borehole volume required to get the cement returns to the seafloor. Many different methods of early detection of cement returns have been used with varying degree of success. Current technologies are very much limited to monitoring the cement returns when boreholes are placed in many challenging areas of deepwater exploration.
For any cementing operation, it is critical to determine the top of the cement column placement. It is also critical to determine the length of the competent cement supporting the casing before further drilling. At present there is no technology available to monitor the cementing operation real time from the time of placement through the entire service life of the borehole. Also there is no reliable method to determine the length of the competent cement supporting the casing.
Here, researchers will enhance the sensing properties of the drilling mud and cementing slurry, so that it can be used for real time monitoring during installation and the entire service life of the deepwater well by incorporating new technologies in the areas of materials and monitoring. Incorporation of new additives to the cementing slurry will make it piezoresistive (change in electrical resistivity with stress, strain, temperature and chemical reactions) from the time of mixing the drilling mud and cement slurry through the entire service life of the hardened cementing material. Advances in materials and grouting technologies will be combined with advancement in surfactant technology to produce drilling mud and cementing materials with enhanced sensing capabilities. With the sensing capabilities installed in the drilling mud and cementing slurry, it will also be possible to monitor the advancement of the drilling mud and cementing slurry front around the casing during the construction phase. The modified drilling mud and cement slurry will have the following characteristics:
- The short-term piezoresistive characteristics will be influenced by the composition, chemical reactions and the surrounding environment (temperature and pressure) causing the changes in internal stresses. Change in stress, strain and/or temperature will cause a change in the electrical resistivity, reflecting the condition of the cement slurry in the borehole. Also the length of cement supporting the casing can be determined accurately.
- The long-term piezoresistive characteristics will be influenced by the stresses induced in the borehole and the condition of the solidified cement materials. It will be possible to identify the locations that are highly stressed in the cemented material. Further other damages caused by the stresses and temperature conditions in the borehole could be identified.
The casing will be modified with outside rings at set spacing to monitor the changes in the electrical resistivity and temperature of the drilling mud and cementing material that are stabilizing the casing and the borehole. The technical study will be completed in three Tasks. In the first task (Task-5- Phase 1), smart drilling mud (SDM) and smart cementing slurry (SCS) will be developed with conductive fillers (solutions and particles) and fibers without affecting the flowability characteristics of the drilling mud or cement slurry. In this Task 5, the SDM and SCS will be characterized based on filtering, fluid loss, piezoresistivity and rock interaction. In Task 6, small and large model tests are planned to demonstrate the potential for the new SDM and SCS. In the final phase a field demonstration will be carried out jointly by the involved parties. Test wells will be identified by Baker Hughes where the process can be fully implemented and tested. Baker Hughes Pumping Services has extensive experience in field trials of new products and services. Past field trials including those where running of an external umbilical attached to external casing hardware have been successfully performed and this expertise will greatly help in the proposed field demonstration study.
Principal Investigators: C. Vipulanandan and R. Krishnamoorti
DOE share: $2,588,900
Recipient share: $1,096,900
Project Duration: 3 years