The Stim-Lab Screen Consortium was formed to study the damage to screens from drill in fluids and formation fines. Initial goals of this study are to examine plugging and cleanup using full size screens in a test apparatus that simulates well bore conditions. The initiation of this study is the result of operators, manufactures, and fluid suppliers asking Stim-Lab to put together an effort which will enhance and compliment the studies which are currently being studied. Stim-Lab invites you to become directly involved... participate in the Stim-Lab Screen Consortium.

Topics of Investigation

Task 1: Literature Review (10%)
A literature review will be conducted in the first few months of the study. The deliverable will be a report in SPE format summarizing what has been done and what is currently being done in the area of screen-fluid interactions and related research. The report was issued in May 1997.

Task 2: Establish Standard Evaluation Techniques (10%)
This task is to provide a set of test procedures and criteria for evaluating screen performance. The deliverables from this portion of the study will be a report outlining various evaluation and classification techniques used by manufacturers, with recommendations on standard testing methods and criteria. The initial report will be issued for comments in May. Members were polled for their opinions and input before the final report was issued in September 1997.

Task 3: Screen Damage and Cleanup Following Insertion (50%)
The objective for task three is to identify and understand the importance of the condition of the hole when the screens are run. This task will evaluate screen damage and cleanup following insertion into drill-in fluids vs: screen type, fluid type, solid type and concentration and cleanup method. A series of 40 tests were run.

Deliverables:

• A compiled report of the results of 40 tests with interpretation. The tests will involve:
  • 5 screens
  • 2 drill-in fluids
  • 2 levels of solids (none and 1% 70-250 sand + rev dust)
  • 2 cleanup methods (enzyme and 10% HCl)
• A set of guidelines for the selection of screen type, fluids, maximum solids, and cleanup methods to optimize screen permeability and life.
• Printed and electronic records of all flow rates vs pressure drop for each phase of each test placed into a database.
• Plots of results for individual and groups of tests.
• SEM photos of selected tests.

The test results will be provided to members on a bimonthly basis. The compiled results of the tests were provided in September 1997.

The procedure used in the evaluation will be as follows:

• Measure the permeability of the test screen with brine and oil in both directions at 120° F for enzyme and acid tests and 180° F for oxidizers. Flow rate will be 331 ml/min to simulate 3 bbl/day over 3 ft.
• Pretest evaluations of the fluid will include API mud rheology, viscosity vs shear rate profile, API fluid loss and particle size of the dirty drill-in fluids.
• Simulate insertion of the screen into the drill-in fluid by flowing the drill-in fluid at a pressure drop of 0 to 200 psi. Flow rate will be 22 gal/min to simulate inserting a screen at 16 ft/min. This is based on a 2-7/8th in. screen in a 6.5 in. I.D. casing. Circulate for 60 min.
• Displace drill-in fluid with brine or a viscous pill. Perform this test in a see-through cell to determine displacement at the selected conditions.
• Determine permeability of the screen to oil in the production direction at 331 ml/min not exceeding a maximum pressure drop of 200 psi.
• Pump in treatment for 10 min. Let soak for 1-4 hours if necessary.
• Displace with brine at for 10 min.
• Flow oil in production direction up to 331 cc/min or a maximum pressure drop of 200 psi.
• Flow synthetic formation in oil and observe change in pressure and report as lbs. sand/sq. ft sand. The rates and loading to be determined by members. In addition, compare this data to baseline data without damage.
• Optional: evaluate methods of cleanup of the plugged screen including flowback methods and chemical methods.

Task 4: Kill Fluid Damage and Cleanup (25%)
The objective for task 4 is to evaluate the placement and cleanup of kill fluids in various screens. The significant damage to the productivity of screens which have been associated with kill fluids was discussed during the meeting. This task will simulate the conditions and then look at the various techniques to remove the damage.

The deliverables of this portion of the study will be:

• A compiled report of the results of 20 tests with interpretation. Proposed tests include:
  • 5 screens
  • 2 kill fluids
  • 2 cleanup techniques
• A set of guidelines for the selection of cleanup method vs screen type and kill fluid.
• Printed and electronic records of all flow rates vs pressure drop for each phase of each test placed into a database.
• Plots of results for individual and groups of tests.

The kill fluid evaluation procedure is as follows:

• Measure the permeability of the test screen with brine and oil at 120° F for enzyme and acid tests and 180° F for oxidizers.
• Simulate placing a kill pill (HEC and Xanvis) into the screen at a 200 psi differential.
• Measure the permeability of the screen to oil in both directions (maximum pressure drop of 200 psi).
• Pump in treatment.
• Let soak if necessary for 4 hours.
• Obtain final permeabilities of the screen to oil in both directions (maximum pressure drop of 200 psi).

Task 5: Evaluate cleanup vs screen and fluids in the presence of formation and filtercake collapse (5%)
The ultimate objective is to evaluate cleanup vs. screen and fluids in the presence of formation and filter cake collapse. The preliminary objective will be to finalize procedural techniques to address these issues on a large scale. Once established, a set of control experiments will be carried out to demonstrate the technique. The group will then decide on what tests will be run.

Deliverables:

• Modified equipment to handle formation and filter cake collapse on screens
• A compiled report of the results of 2 control tests with interpretation. Proposed tests include:
  • 2 screens
  • 1 drill-in fluid
  • 1 cleanup technique

The modifications and control tests will be completed by the year-end meeting.

Consortium Membership
The Screen Consortium has included the following:

Equipment
Stim-Lab possesses all the necessary equipment to properly conduct the outlined screen testing. This equipment includes both field and laboratory size pumps and mixing equipment. Figure 1 shows an overview of some of this equipment.

Mixing equipment consists of frac tanks, a blending unit, intensifier pumps, and a heated coil tubing unit . For this study fluids will be mixed in either a 1000 gallon stainless steel mixing tank, two 600 gallon mixing tanks lined with a protective ceramic coat, or a combination of six 55 gal portable mixing tanks. In addition, a smaller scale mixing skid is capable of pumping solids at rates of 0-2 gal/min.

The base DIF (drill in fluid) will be mixed using the 1000 gal stainless steel tank by circulating with a centrifugal pump which is mounted between the blender and the fluid tank. As water is circulated, the base polymer is added. After mixing, the rheology of the fluid is characterized on a Fann 35, Fann 50, or a low shear rheometer. Additional measurements such as API fluid loss and particle size distribution can also be determined. After fluid preparation, one of 12 pumps, depending on the rates, are used to pump the fluids to the screen model.

A heat-up/conditioning simulator will be used that consists of 3000 ft of 1 in. coil tubing in a water bath. The internal diameter of the tubing is 0.89 inch. A flow rate of 0.6 bbl/min corresponds to a velocity of 13 ft/sec and a Reynolds number of 89,500 for water and 5000 for gel.

Two test models for running screen evaluations on a large scale currently are constructed. One model is constructed of 316 stainless steel pipe casing. It has removable ends and is 6.5 feet in length with an internal diameter of 7 inches. This model is designed to house a 2-4 ft long screen which can be decentralized. Longer screen lengths up to 5-1/2 ft can be utilized in a centralized geometry.

The second model is constructed of Lexan and is in. It has the same length and internal dimensions as the stainless steel model and can handle pressure up to 500 psi. This model will be used for testing where the fluid mechanical and displacement issues are of consideration. Currently, only low temperature tests will be conducted with the clear model. All tests will be filmed with in-house video equipment for video presentation of the results.

The screen testing equipment will be modified for task 5 to handle filter cake and formation collapse.

During a test all of the pertinent data is sent to a data acquisition computer located in the control room which is capable of recording temperatures, pressures and flow rates. The flow rates are measured with either turbine or micromotion mass flow meters. The pressures are measured with smart pressure transducers.

The field scale mixing unit is composed of a high pressure, triplex pump capable of pumping from 0 to 9 barrels per minute up to 10,000 psi, a solids addition system which allows preparation of muds and slurries on the fly, and a stainless steel mixing tank.

The mixing skid is capable of pumping from 0 to 1 gallon per minute, at pressures up to 1,000 psi, and also has the ability to pump solid-liquid slurries.

Membership to the Stim-Lab, Inc. Screen Consortium
Stim-Lab encourages new members so that research continues adding value to participating company's lines of business. Membership grants access to the "members only" web site which contains research updates, reports for download, plus any programs or spreadsheets developed within the program.

Contact Us  for membership information.