HTHP

A drilling fluid HTHP (High Temperature High Pressure) procedure involves heating a sample of drilling fluid to a specific temperature simulating downhole conditions, then applying pressure to measure the amount of filtrate (fluid that passes through a filter) collected over a set time, essentially evaluating the fluid’s ability to resist fluid loss under extreme temperatures and pressures in a wellbore; this test is typically conducted using a specialized HTHP filter press apparatus, where the fluid is heated within a cell, and pressure is applied to monitor filtrate volume and filter cake thickness.

Key steps in a drilling fluid HTHP procedure:

Sample preparation:

Obtain a representative sample of the drilling fluid. 

Loading the cell:

Fill the HTHP filter press cell with the fluid sample, ensuring appropriate volume to account for expansion at high temperatures. 

Temperature setting:

Set the desired test temperature on the heating jacket of the HTHP filter press, which should match the expected downhole temperature. 

Pressure application:

Once the fluid reaches the desired temperature, apply the specified differential pressure to the cell using the pressure regulator. 

Filtration process:

Initiate filtration by opening the outlet valve and collect the filtrate over a predetermined time period (usually 30 minutes). 

Procedure

  1. The HTHP jacket is preheated to 10°F (5.6°C) above the test temperature.
  2. Add the test fluid to the test cell and prepared for testing.
  3. A thermocouple is placed into the top portion of the test cell.
  4. The test cell is placed in the preheated jacket.
  5. Top and bottom pressure regulators are connected. Nitrogen gas is applied through the top valve at 100 psi (690 kPa).
  6. The pressurized test cell and fluid is allowed to heat for 60 minutes.
  7. At the end of 60 minutes, the pressure on the top regulator is increased to 600 psi and the bottom receiver pressure is adjusted to 100 psi, resulting in a 500-psi differential pressure across the filter paper.
  8. The bottom test cell valve is opened to start the test.
  9. After 30 minutes, the bottom valve is closed to end the test.