Fiberglass sucker rods (English version)
Fiberglass sucker rods
It is a well-known fact that oil production at the majority of large oilfields is continuously declining. Wells at such oilfields typically demonstrate decreasing flow rate and growing water content. Moreover, it also lowers the cost effectiveness of product recovery. This situation requires special countermeasures to be taken, such as reducing the power consumption of product lifting operations and extending the time between overhauls (TBO).
According to downhole pump assembly failure statistics, about 20-30% of downhole pump failures on the average are caused by sucker rod breakage. In 70-80% of the cases, the breakage location is within the rod body. The main breakage causes are rod body corrosion and heavy loads on the rod string.
Promtechkomplekt, as part of its petroleum equipment production and supply program, produces and delivers fiberglass sucker rods (FSR) for transferring motion from pumpjacks to downhole plunger pumps. The rods are made in cooperation with the Biysk Fiberglass Factory.
Fiberglass has the following physical differences from steel:
- fiberglass density (1900 kg/m3) is about 4 times less than that of steel (7850 kg/m3);
- fiberglass modulus of elasticity (50,000 MPa) is approximately 4 times less than that of steel (210,000 MPa);
- fiberglass roughness coefficient (0.0015) is about 20 times less than that of steel (0.03);
- high corrosion resistance;
- no plastic deformation, any deformation taking place in the rod body is the elastic type.
- reduced maximum load on the horsehead during rod string lifting;
- the downhole pump suspension depth may be increased to 2500 m;
- reduced amplitude and dynamic loads;
- no corrosion or paraffin deposits;
- decreased power consumption of surface equipment.
Our fiberglass sucker rods have a guaranteed service period of 12 months (twice as much as GOST R 51161-2002 steel sucker rods (6 months)) and feature 7.5 million base cycles with a survival function of at least 0.995 (as compared to 5 million cycles for the steel rods).
The fiberglass sucker rods made to specification TU 3665‑023‑20994511‑2010 have the following approvals and comply with the requirements of:
- GOST R 51161-2002;
- GOST 12.2.003-91;
- Technical Regulation "On Safety of Machinery and Equipment";
- (the GOST and TU requirements are harmonized with API Specification 11 B).
|As of , our fiberglass rods have the following operating times (by wells):|
|Well||Date of commissioning||Operating time, days|
|#1034, Chutyr oilfield|
|#1205, Chutyr oilfield|
|#739, Mishkino oilfield|
|#727, Mishkino oilfield|
|#1929, Mishkino oilfield|
Fiberglass sucker rods help reduce oil production costs.
According to Russian and foreign sources, the main benefits of fiberglass sucker rods are:
- reduced rod string weight;
- high corrosion resistance;
- extended operating life (by 5 to 6 times);
- increased flow rate (up to 75% on the average);
- maximum load on the polished stem reduced by 30% on the average;
- the downhole pump may be installed at a depth of 2000 m or even more.
Our fiberglass sucker rods have the following design.
The FSR consists of the body (a fiberglass stem with centralizers) pressed into the head (a steel part). Sucker rods are connected into a string using steel couplings. The metal head may be made of a grade D strength material.
Main benefits of fiberglass sucker rods over steel rods
- increased production;
- less prone to breakage (no breakage cases due to FSR failure were observed during the pilot testing);
- less paraffin depositing;
- electric energy savings (over 1 kWh per well demonstrated during the pilot testing);
- the ability to use fiberglass tubing.
The pilot testing of fiberglass sucker rods was carried out at Udmurtneft oilfields,
using the following efficiency assessment criteria:
- an increase in the well operating time to failure due to sucker rod breakage, as compared to the previously used standard metal rods;
- a reduction in load on the pumpjack horsehead;
- the ability to increase the downhole pump depth within the allowable range of reduced stress on the FSR string, as compared to the previously used standard metal rods;
- no failures due to FSR breakage during the pilot testing.
The fiberglass sucker rod weight is 3 times as less as that of a steel rod. The special design of the FSR package allows for transporting up to 1000 ShNS 25-8000 rods (with a rod body diameter of 25 mm and a rod length of 8 m) in a standard Euro trailer. No special equipment or accessories are required for FSR loading and unloading.
Fiberglass sucker rod sizes per specification TU 3665‑023‑20994511‑2010;
|Dimensions||Standard rod size|
|3/4” (16 mm)||7/8” (22 mm)||1” (25 mm)||1 1/4” (29 mm)|
|Rod length L±50, mm||8000; 6200 (6100*); 7620 (7518*); 9140 (9042*)||Short rod length L±50, mm||450; 610; 915; 1220 (1118*); 1500; 1830 (1727*); 2440 (2337*); 3050 (2946*); 3660|
Fiberglass sucker rod weight,as compared to steel rods.
|Standard size||Rod weight, kg, by length, mm.|
|3/4” (16 mm)||7.1/17.9||7.3/18.7||7.9/21.3||9.0/-|
|7/8” (22 mm)||9.0/24.4||9.3/25.3||10.2/29.0||11.8/-|
|1” (25 mm)||10.6/32.1||11.0/33.1||12.1/38.0||14.2/-|
|1 1/4” (29 mm)||13.2/41.3||13.7/43.2||15.2/49.0||17.8/-|
Number after slash: weight of steel sucker rod, kg.
Fiberglass sucker rod specifications per TU 3665‑023‑20994511‑2010
|Rod head material strength grades and specifications|
|Strength grade||Yield strength|
σy, MPa, min.
|Ultimate tensile strength|
|Mechanical specifications of rod stems|
|Ultimate tensile strength
σUTS, MPa, min.
|Modulus of elasticity
E, MPa, min.
|Operating temperature, °C||Low temperature limit, °C|
Fiberglass sucker rod commissioning video.
Promtechkomplekt and Udmurtneft signed a maintenance contract, according to which the representatives of our company as the rod manufacturer should witness the lifting of fiberglass sucker rod strings. On June 14, 2011, our experts witnessed the lifting of a rod string for subsequent overhaul at well 1205 of a Udmurtneft's field. Visual examination revealed that the string breakage location was within a steel sucker rod ShN22 (sucker rod 7/8”), and the probable cause of the failure was heavy corrosion of the rod body. The breakage location and condition of the ShN22 (sucker rod 7/8”) steel rod body are shown in Fig. 1. The manufacture date and strength grade are shown in Fig. 6 and Fig. 7.
Fiberglass rods that had been in operation at the same well for over 220 days (for the same period as the steel rods) demonstrated no visible changes. (A 50/50 mix of fiberglass and steel rods was used.) No paraffin deposits or visible wear of rod components (end fitting, body, centralizer) was found during the visual examination, see Fig. 2-5. The well workover personnel told us that they would like to continue using fiberglass rods.
On March 28, 2012 our representatives witnessed the emergency lifting of a sucker rod string at a well equipped with fiberglass and steel sucker rods (a 50/50 mix). After lifting the downhole pumping equipment, no damage or discontinuities were found on fiberglass sucker rods, while steel sucker rods showed signs of significant corrosion-related damage. The examination results were documented.