Wire Wrapped Screen Pipe for Gravel Packing
A wire wrapped screen consists of a perforated base pipe and a wire wrap jacket that is wrapped around the outside of the base pipe. The wire wrap jacket is made up of multiple layers of wire that are wrapped at an angle around the base pipe to form a continuous spiral pattern. The wires are wrapped tightly together to form a strong and durable structure that provides filtration of the fluid while allowing it to flow through the perforations in the base pipe. The size and spacing of the wire wrap jacket can vary depending on the specific application and filtration requirements.
The gap or slot size of a wire wrapped screen is typically determined based on the grain size distribution of the formation or reservoir being drilled. The objective is to select a gap size that will allow fluid flow while preventing sand and other solids from entering the wellbore.
The most common approach to determining the appropriate gap size is to use the Darcy's law formula, which relates the fluid flow rate to the pressure drop across the formation. The following steps are typically followed:
-
Obtain the particle size distribution (PSD) data for the formation or reservoir. This data can be obtained through laboratory analysis of core samples or cuttings.
-
Calculate the median grain size (d50) of the PSD. This is the grain size at which 50% of the particles are smaller and 50% are larger.
-
Determine the hydraulic conductivity (K) of the formation. This can be calculated using Darcy's law and the measured pressure drop across the formation.
-
Use the following formula to calculate the slot or gap size (s) of the wire wrapped screen:
s = K / (100 x d50)
Where:
- s: Slot or gap size in microns
- K: Hydraulic conductivity of the formation in millidarcys
- d50: Median grain size of the formation in microns
