Preventing String Integrity Failure in Production and Stimulation for High Temperature Wells
- Gama Hafizh Aditya (EMP Malacca Strait) | Edy Subiantoro (EMP Malacca Strait)
- Document ID
- Society of Petroleum Engineers
- SPE Asia Pacific Oil & Gas Conference and Exhibition, 14-16 October, Adelaide, Australia
- Publication Date
- Document Type
- Conference Paper
- 2014. Society of Petroleum Engineers
- String Integrity, Selective completion, High Temperature, Hydraulic Fracturing
- 1 in the last 30 days
- 96 since 2007
- Show more detail
- View rights & permissions
|SPE Member Price:||USD 9.50|
|SPE Non-Member Price:||USD 28.00|
String integrity is essential for successful production and stimulation.
With production, string integrity means pressure integrity of packers and sliding-sleeve-doors commonly used to isolate target production zones. With hydraulic-fracture stimulation, frac-string integrity is mostly concerned with the burst pressure of the string, packer load and string friction, which depend on fluid rate and pump pressure.
In high-temperature wells, things get more complex. High rate producers heat the production string far above the normal gradient temperature, and so it expands. With frac strings, the opposite occurs. Injected water cools the string far below the normal gradient temperature, and so it shrinks. Both situations create additional string integrity issues.
In 2008, EMP Malacca Strait drilled and completed (as selective singles) three infill wells in Kurau, a mature oil field in Sumatra, Indonesia. Later, when changing ones, the completion string was found to be buckled. An impression Block showed an obstruction inside the tubing. This zone could not be changed.
In the same year, we performed our first hydraulic-fracture-stimulation campaign in the Kuat oil field, of sandstone reservoirs at 320 degF. During the first job, the frac string failed during the data-frac, as seen by the sudden increase in annulus pressure. We suspected the packer unset due to high shear load from frac-string thermal shrinkage.
Both these string failures occurred, despite standard shrinkage calculation suggesting there should be no issues.
The paper investigates elongation and shrinkage of production and frac strings using a finite difference-mathematical model. The study found a much higher thermal expansion factor than from a standard calculation, and so we started to use expansion joints for both selective completions and for fracture-stimulation campaigns.
Since this time, we have suffered no further string failures.
Malacca Strait PSC was located in the Eastern part of Riau Province, Sumatra, Indonesia. It is in the Central Sumatra basin, as seen in Figure 1. This basin has the highest temperature gradient in Indonesia; up to 7 degC/100 meters. The PSC contains five major fields:Kurau, Kuat,Melibur, Selatan and Lalang/Mengkapan. This paper deals with the Kurau and Kuat oil fields. In 1984, production started in the Kurau Field fromdarcy sands at around 5000 ft. The completions produced several sands commingled and lifted liquids with Electrical Submersible Pumps (ESP). Initial rates were around 5000 bopd under a strong water drive. These days, the wells flow 10’s to 100’s bopd have with high water cuts of 95% to 99%.
|File Size||4 MB||Number of Pages||8|