Experimental Investigations And Field Observatnons On Mechanisms Of Solids Filtration Using The Meshrite Metallic Wool Filter
Authors: Toma P. , Korpany G.G. , King R.W. 
Published: March 2010

A new sand control filter made of a pre-packed steel wool was designed to achieve a better control of solids influx for horizontal and vertical wells exposed to high-temperature recovery processes.

An experimental laboratory study using Athabasca and Lloydminster formation samples was conducted in order to quantify the influence of filter depth and compression on the efficiency of the sand filtration-retention process and simulate a set-through completion. A model capable of predicting the amount of fines retained outside the filter, as well as those accumulated and produced during a standard flood process, is suggested on the basis of experimental data using Athabasca unconsolidated formation. The model is further used for assessing the influence of the design of a sand control device and the near-well formation characteristic in retaining fines during the production process.

Introduction

Controlling the production or sand in thermal and conventional unconsolidated oil fields is a critical component of engineering the well completion and production facilities, The high cost associated with well servicing and the considerable reduction of oil produced due to well sanding and plugging are among the most frequently encountered production problems(1,2,3). The frequent interruption of production associated with well servicing also disturbs the thermal process and may induce unpredictable formation damage.

To alleviate problems related to sand production, new strategies are being continuously investigated. They focus on improving drilling operations, consolidating the near-well formation, and finding the most suitable well completion method including gravel and screens in combination with suitable adjustments of the rates of injected and produced fluids.

Two distinct strategies have been suggested for sand control: total exclusion and partial exclusion of sand from the production system. It appears that each strategy has its own merits and drawbacks.

If partial exclusion is adopted, efficient methods for eliminating the sand accumulated in the production system, including suitable artificial lifting devices, are still required; erosion reduces the life or production equipment considerably. It appears that a certain amount or sand production is beneficial to increasing the oil recovery, especially in the heavy and extra-heavy oil reservoirs where permeability and production increases are associated with moderate sand production.

Total exclusion achieved through sand retention in the near-well region and in the filtration equipment will undoubtedly protect the production system from erosion, and reduce the risk of the near-well formation collapse. However, total exclusion could result in progressive plugging or the filter and deterioration of the productivity index.

The most common methods of excluding sand utilize screening or a combination or screening and filter pack. They involve: slotted or screened liners; and packing of the hole with aggregate such as gravel.

A basic requirement of these methods is to design the slots to retain the gravel which has been selected to hold the formation in place. Difficulties in properly placing the gravel (especially in horizontal wells), or in avoiding a rapid dissolution of gravel in a high-temperature and alkaline environment specific to steam operations, necessitated the use of slotted or screen liners with the opening designed to directly retain the formation.