Downhole equipment hydraulic testing

HFL-150 hydraulic bench

Hydraulic testing is one of the most important areas to determine the quality of downhole equipment. The testing determines characteristics such as collapse/tensile strength, erosion resistance, and discharge characteristics of inflow control valves. The main testing bench is the HFL-150 hydraulic circuit bench.

The hydraulic bench specifications:

The hydraulic circuit maximum pressure is 170 atm (~2500 psi).
The working fluid viscosity is up to 1500 cP.
Concentration of solid abrasive (sand form) (SSC) up to 1% (10000 ppmw).
The working fluid temperature is 10-60⁰
The maximum abrasive particle size is 500 microns.
Maximum circuit flow rate 50 l/min (3 m3/h) at 140 bar.
Conical vessel with a stirrer (working fluid for 0.5 m3).
The test capsule for the screen sample is 4 ½ " and the outer diameter of the winding is 130 mm. The working capsule’s outer diameter is 168 mm.

Bench automation system includes:
- Frequency converter (inverter) of a hydraulic pump
- Cooling control system
- Emergency control system.
The parameter registration system includes:
- Inlet and outlet capsule pressures.
- Mass circuit fluid rate.
- Fluid density.
- Fluid temperature.
- Fluid level in the storage tank.

HFL-150 hydraulic bench

The design of the hydraulic bench includes a hydraulic suspension pump, a test capsule for the testing sample, a conical tank, a Coriolis flow meter, pressure and temperature sensors, hydraulic throttles, RVD, fittings, shut-off valves and an automation system. The working fluid flow in a contour allows for multi-day long tests.

A modification of the HFL-150 hydraulic circuit bench allows the implementation of collapse/tensile sand screen testing.

Flow Performance Tests

Flow performance testing is to determine the flow rate specification of inflow control devices. Flow performance testing is performed with different viscosity values of fluid. The HFL-150 hydraulic circuit bench is used to perform these tests. The testing is generally performed on water and oil with a dynamic viscosity given value. The testing methodology is based on API Specification 19SS, 2019.

Because fluid viscosity is highly dependent on the temperature of the fluid in the hydraulic circuit, it is important to control its temperature. The testing sample pressure drop, as well as, the total inlet pressure level in the test capsule are the characteristics of flow performance testing. The result of the testing is the testing sample flow curves constructed depending on the pressure drop. Different curves of the dependencies are constructed for different fluid viscosities.

Working scheme in testing period:

Installing the testing capsule
Assembling hydraulic connections
Filling the hydraulic system with the working fluid.
Check all connections for leaks
Air removal from the hydraulic circuit.
Setting the working limits for control system parameters. Outside the working limits of most values is considered as an emergency situation and should lead to a shutdown of the testing bench. The following working limits characteristics are provided:
- The minimum fluid level in the conical tank.
- Pressure drop limits.
- Mass flow rate value limits.
- Fluid temperature limits. When the upper value of the limit is reached, the circuit cooling system is switched on, when the lower value is reached, it is switched off.
Adjust the pump speed and the needle valves (throttles) to achieve the required pressure difference at the inlet/outlet of the testing capsule.
Testing starting and running.
Analyzing the accumulated data on the sensor readings, data graphing, and generating a testing report at the end of the testing.

Mechanical wire wrap separation testing (Weld Separation Test)

The testing task is to verify the resistance of sand screeners, and control and injection valves to erosive wear and the exploitation possibility in difficult oil and gas field conditions. The erosion testing task:

• To conduct testing following API Specification 19SS, 2019 quality standards.
• To determine the operation possibility of downhole screens and BOP and injection valves at hydrocarbon resource development facilities.
• To verify the erosion resistance of downhole screens and BOP and injection valves.
• To decide on supply equipment for serial production following the results of the testing.

Erosion testing on the HFL-150 bench

To create an erosion environment, abrasive (sand-laden) at the desired concentration is added to the working fluid. Due to simulating the conditions of long-term use of the equipment in the well, the testing is performed over a long period of time. The duration estimation depends on the options of abrasive concentration in the working fluid.

We follow the recommendations of API specification 19ICD Inflow Control Devices (2019).
The erosion testing methodology involves performing flow performance testing before and after performing the erosion test. To evaluate the effects of erosion wear on the testing assembly by measuring the flow characteristics of the valve during flow performance testing.

In the case of erosion testing, to the working scheme of flow performance testing following operations are added:

• To add abrasive in concentration according to the test specification.
• The testing is stopped either when the scheduled testing has finished or when the system parameters leave the specified corridors. If the pressure and flow parameters are out of the specified limits, it can be regarded as an erosion valve failure.

Before removing from the device, the testing valve must be weighed before and after the erosion testing to evaluate the effect of erosion on the valve weight. The condition of the valve also must be photo-fixed and analyzed before and after the tests.

Hydraulic collapse tensile testing (Burst&Collapse Test)

Hydraulic diagram of the burst/collapse testing

The sand screen construction strength is tested more than only mechanical tests. It is required to determine downhole sand screen strength to large-pressure differentials. Hydraulic tests for screen structure burst and collapse are carried out for the testing. Modification of the HFL-150 hydraulic bench is used for these tests. The hydraulic scheme uses two colmatant tanks for the testing. The testing screen sample is placed in the special testing capsule of large size (273 mm outer diameter). The hydraulic bench scheme with an open circuit for the fluid.

A special technical liquid formula solution is selected for the colmatizating of the screen sample in the high-pressure test capsule. The solution must be well mixed, contain calcium carbonate with particle size fractions, xanthan gum, and starch to create a highly viscous medium. The screen with the solution under pressure in the testing capsule is colmatized. The main task of the testing is to check the screen strength at high burst/collapse pressures with a colmatized solution.

The mini hydraulic laboratory bench is used for the required solution preparation. It verifies the colmatation properties of the solution through a wire-wrap screen coupon.
Tests are performed according to API Specification 19SS, 2019. With the connection of flexible supply hoses, the bench could be used in two configurations. The pressure is applied to the outside of the testing sample; on the contrary, the pressure is applied inside the borehole screen sample for the bursting testing. Hydraulic testing requires preparatory work to build up a reserve of colmatated fluid and to install the screen sample on the test bench. The result of the test is a confirmation of the screen’s strength parameters under high-pressure conditions.

Work scheme:

To prepare the testing colmatation solution according to the basic formulation.
To test the colmatation properties of the solution on a mini-bench based on the testing screen wire-wrap coupons. To change the solution formulation to achieve the required characteristics.
To prepare the required volume of colmatation solution according to the developed formulation.
To prepare the testing screen sample.
To install the sample in the working capsule of the bench.
To mount connecting hoses of the bench. To fill the colmatant tank.
To connect the hydraulic slurry pump to the bench.
To start the testing program. To increase slowly the pressure in the chamber to the target values. To register the different points of pressure values of the hydraulic circuit and colmatant flow rate.
When the maximum pressure of the test program is reached or if there is a breakdown in the testing screen, stop the test process and depressurize the system.
The result is the conclusion of the hydraulic testing.

The hydraulic bench specifications:

Max working pressure up to 200 atmospheres
The capsule length – 4000 mm
Capsule diameter – 273 mm
Capsule weight – 3550 kg
Screen sizes – 4 ½; 5; 5 ½; 6 ⅝; 7 "
Maximum system flow rate – 2.8 m3/h

The operator conducts hydraulic tests in the protected area located in the bench control system.