Monitoring and Analysis of ECP Inflation Status Using Memory Gauge Data
- Huawen Gai (BP Exploration) | Grahame Elliot (BP Exploration)
- Document ID
- Society of Petroleum Engineers
- SPE Drilling & Completion
- Publication Date
- September 1997
- Document Type
- Journal Paper
- 203 - 207
- 1997. Society of Petroleum Engineers
- 1.10 Drilling Equipment, 1.11.2 Drilling Fluid Selection and Formulation (Chemistry, Properties), 1.6 Drilling Operations
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The current surface instrumentation for monitoring the ECP (External Casing Packer) inflation status has been identified as unsatisfactory. This is responsible for a significant degree of uncertainty in the evaluation of ECP performance. Coupled with some unreliable practices in the installation process relating to the use of the instrumentation, the data interpretation is often difficult.
To combat the inaccuracy of surface measurement, memory gauges have been used downhole in West Shetland for the first time as a retrospective tool to monitor ECP status. The memory gauges, mounted on the work string and close to the ECP, remove the damping effect of the fluid column in the work string and are capable of measuring the squeeze pressure below the ECP due to inflation. It is demonstrated in these operations that the following has been achieved:
- Identified the ECP status unambiguously and reliably in several wells;
- Identified some problems in job design such as hydraulic lock, which may result in partial inflation, and incorrect setting of pressure shear-pin levels for inflation leading to the formation being fractured;
- Gained insight in pipe movement induced swabbing and pressure surge which adversely act on the formation. Certain information on the mud such as solid settlement and pressure-volume relations were also obtained. - Gained valuable data (both from the memory gauges and the surface gauges) which have set a corner stone for setting certain guidelines in interpreting ECP status by surface instrumentation.
Detailed analysis of the data with examples and case histories are presented. Key considerations in operations and lessons learnt together with recommendations are then discussed before the conclusions.
ECP status monitoring was identified as a problem area and confirmed by a general study. Ambiguity immediately after the installation and contradiction to report of successful inflation later often result. There are sufficient data to show that ECPs indicated at surface as "properly inflated" do not provide a seal in the annulus. This has been accepted by all the major ECP manufacturers.
There are two main causes for this: unsatisfactory instrumentation and some unreliable practices in the installation process relating to the use of the instrumentation.
Evaluation of ECP installation status is achieved through surface pressure and pump volume indications. The current monitoring instrumentation is mostly pressure gauges only, typically of mechanical type at surface such as a Martin Decker. Packer opening would be reflected in the pressure drops in the charged system, i.e. the pump, the lines linking to the well, the well bore or work string which connects to the inflation ports of the ECPs. Packer inflation volume, however, is still mostly gauged by human eye of the fluid tank level. It is perhaps not surprising that such a combination often results in ambiguous indication, especially when the fluid volume in the well bore or work string is large with a high compressibility coefficient (of the order of 3x10-6 psi or higher), and the inflation volume is small (e.g. <0.2 barrel).
|File Size||337 KB||Number of Pages||5|