Viable alternative to horizontal gravel packing
Shell Exploration & Production Co.
Halliburton Energy Services Inc.
The expansion tool used in the system consists of three parts – the slip section, the power section, and the cone section.
Well screens are used in the open-hole-producing zone of a horizontal well to provide filtration to prevent sand production. After the well has been on production for a period of time, the formation can become somewhat unstable. This condition can result in excess sand production and hole-sloughing, which can cause plugging and subsequent erosion of the screens. In some cases, significant external loads can be applied to the screen as a result of wellbore collapse. These external loads can collapse the screen if it does not have sufficient structural integrity.
The system includes a screen, running tool, screen hanger, and screen-expansion tool.
To provide the best level of sand control and wellbore support, the annular space between the screens and wellbore can be gravel packed. To create a reliable horizontal gravel pack completion with a high probability of success is difficult in some well conditions. Also, the installation of a sand-control screen reduces the production inside diameter (ID) that is otherwise available, and designing for gravel pack placement around the screen can reduce the ID still further.
An expandable filtration system with enhanced collapse-strength integrity was chosen as the appropriate solution for this problem. If this system could be successfully developed, the following measurable results would be realized:
- Reduced failure rate due to elimination of hot spots (erosion) over time
- Increased hole size for re-entry and work-over capabilities
- Increased production rates
- Possible reduction in bore size for drilling-cost reduction
- Improved reliability due to greater installation success
- Installed cost comparable to horizontal gravel packed wells.
Because of the complexity of the solution and the commitment required, the decision was made to use the product development and commercialization (PD&C) method for this project. The PD&C method involves the creation of a development team made up of technology personnel who are entirely dedicated to the development of the product. In addition, representatives from manufacturing, procurement, sales, and operations are included on the team.
By having participation from personnel with varying areas of expertise during the project design, the team achieved creative, cost-saving solutions and reduced development time significantly.
A firm understanding of customer needs during the design process ensures that new products meet market demands. For that reason, several key customer contacts were also involved from the initial stages of the project. These individuals have provided input pertaining to product requirements and suitable test regimes. The added step of customer involvement in the process ensures customer acceptance during the performance verification and commercialization phase.
When the project reached fruition, the completed product was an expandable sand screen that can be expanded inside a 6 1/8-in. open hole and provide sand control during production. The system includes a screen, running tool, screen hanger, and screen-expansion tool.
PD&C process outline
The PD&C process begins with needs identification. The ideas for new products and services can originate from anywhere within an organization or from its customers. A brief product review determines the merits of an idea and whether it warrants being included in the PD&C process. Ideas that can be considered to have commercial or technical justification may require a feasibility assessment first or can move directly to a product development team.
The development of the expandable screen system followed the general steps outlined for bringing all PD&C strategies to fruition:
- Feasibility assessment involves analyzing the findings from the opportunity identification and evaluation process. During this phase, a preliminary project plan is prepared. The plan typically includes the project scope, functional specifications, technical risks, market analysis, and parameters for economic justification
- The concept development phase begins with the team's identification of specific customer requirements and expected outcomes. The team then search-es for potential solutions to satisfy identified needs and completes a justification for the best solution. Finally, the field project development (FPD) team prepares a detailed project plan, which generally includes design verification and field testing
- The design of the new product is accomplished and documented during the project design phase. Then, laboratory testing of the resulting prototype product to ascertain compliance to the original requirements and specifications takes place. The design-verification phase is followed with detailed plans and documentation for field-testing. At this point, a product champion is usually selected to work with the FPD team to assume responsibility for implementing the commercialization plan
- For the expandable screen system, the preliminary testing plan included the following: screen expansion tests, screen burst and collapse tests, expansion-tool testing, and overall system testing
- During the field test phase, product performance is evaluated against defined product specifications by testing in conditions that will represent the natural operating environment of the product. In addition, the final supplier evaluation will be completed, and partnerships or alliances established for future needs.
Expandable screen design
The development team started initial physical testing to confirm design assumptions and to verify the finite element analysis (FEA) technique being used. The initial questions concerned were where resources should most efficiently be spent. The first FEA results were not of sufficient accuracy or speed to be useful as a design tool because the FEA test runs did not match physical testing results for plastic strain, force, and failure data.
In spite of the less-than-satisfactory initial results, the team thought that it would be worthwhile to continue to develop the FEA as a design aid. When the modeling techniques and material properties were improved, the FEA results were verified against physical testing, and the technique became an accurate and significantly useful tool. The team now uses FEA as a method for minimizing testing, improving reliability, verifying material choices, and helping to identify design improvements.
Final screen candidates
A number of design ideas for an expandable screen were examined during the concept development phase. The most promising ideas were pursued simultaneously so that the best concept could be determined and its development pursued in the most time-efficient manner. During this initial evaluation process, each concept was compared on the basis of expansion performance, manufacturability, and filtration capability after expansion. The final candidates were the micro-slotted screen, the wire-wrapped screen, and the sintered laminate filter media screen.
The expansion tool used in the system consists of three parts – the slip section, the power section, and the cone section. As pressure is applied, the slips engage the inside diameter of the tubing, and the power section produces the force required to expand the screen. The cone section consists of an expandable/retractable cone that expands the pipe and screen simultaneously.
After the system components were found to perform satisfactorily to specification, the complete system was tested in the development facility's test well. The first well test provided a performance evaluation of the expandable screen system, including the expansion tool, liner hanger, basepipe, screen, and thread connection. During this test, about 100 ft of material basepipe, screen, and thread connections were expanded. The length of the expandable joints was 11 ft so more thread connections could be included for expansion.
The second well test offered further evaluation of the expansion tool, base pipe, screen, and thread connections. During this test, about 150 ft of range three joints were expanded. The development team, which included representatives from the operator, witnessed the test.
Burst and collapse testing
Screens are sometimes exposed to internal and external pressures during well completion and production. If the screen is plugged externally, and the wellbore pressure increases, it will be subjected to collapse pressure. The screen may be subjected to burst pressures if it is plugged-off so that it will allow pressuring up on the tubing.
Extensive testing was performed to define the internal and external pressure limits. Numerous assemblies were tested in the unexpanded and post-expanded configurations. Average actual burst pressure in the unexpanded condition was 839 psi and average actual collapse was 4,000 psi. Average actual burst in the post-expanded configuration was 1,200 psi, and actual average collapse was 3,100 psi.
Relatively thin wall tubing and relatively low yield strength was necessary on expandable screens to allow lower expansion forces. There was concern that the burst and collapse ratings would be unacceptably low when compared to established screen configurations, therefore, comparison tests were conducted.
The expandable thread was also tested in burst and collapse. Expanded collapse pressure was 2,250 psi and expanded burst pressure was 6,500 psi. Unexpanded collapse was 4,000 and unexpanded burst was 5,800 psi. Burst mode of failure was the thread jump-out in all but one case.
If the screen is plugged externally, and the wellbore pressure increases, it will be subjected to collapse pressure.
The first customer trial run for the expandable screen system was conducted at Shell's Hinojosa 8 in the Fandango field onshore Texas. An expandable liner hanger was used and was set at 3,300 ft in 9 5/8-in., 43.5 lb casing with about 9.5 lb/gal mud in the borehole.
The first well test provided a performance evaluation of the expandable screen system, including the expansion tool, liner hanger, basepipe, screen, and thread connection.
Two trips were made during the installation of the expandable system – the first to set the hanger system, which places the screen in the correct position, and the second to perform the actual expansion process.
After the hanger was successfully set, the running tool was pulled, and the expansion tool was picked up. The expansion tool, 4 3/4-in. drill collars, and 4 1/2-in. work string were run to depth. The cone on the expander tool no-go'ed on the cone launcher, and the string was picked up 12 ft. Pumps were rigged up, and circulation started. After returns were seen at the surface, the rate was increased to deploy the cone on the mandrel to the expansion outside diameter.
Pressure was bled off, and the expander tool was run in the hole until it again no-go'ed on the cone launcher. The pipe was marked, and pumping started again. Pump rate was increased until the tool stroked, and pumping was stopped. The work string was lowered into the well, and the distance stroked was recorded. This process was repeated.
On the sixth cycle, the tool did not stroke at the same pressures as previous cycles. After a review of the tally and additional attempts to stroke the expansion tool, it was determined the tool was at a screen weld on one of the joints. The pressure was increased to 4,500 psi, and the tool stroked. On the last stoke, the tool moved the last 5 ft, the seals stung into the mandrel, and the tool sheared out. The expander tool was then pulled out of the hole and inspected.
The expandable screen system performed as expected. About 160 ft of screen and basepipe were expanded in 20 cycles. The expander tool expanded the desired interval with no failures. Expansion pressures typically ranged from 3,600 to 4,200 psi with one cycle spiked up to 4,500 psi. A caliper log verified a 5.44-in.-ID after expansion.
A new expandable screen has been developed to provide a solution to prevent hole-sloughing and sand production in horizontal wells. Laboratory testing has shown that the expandable screen possesses acceptable collapse and burst resistance. Results of the system testing and the field trial have shown that the expandable screen can be a reliable method for controlling sand production and hole sloughing in horizontal wells. This technology offers a viable alternative to horizontal gravel packing, and in some environments, the expandable screen system may prove to be even more effective in controlling sand production than gravel packing.
The PD&C method was successful in bringing the expandable screen to market in the shortest time possible. Design and manufacturing issues were addressed concurrently rather than sequentially during the various phases of the project. This method enabled both the design and all manufacturing processes to be proven during system testing prior to introduction to the field.
The expandable screen has also been developed for the 8 1/2-in. open-hole using the same technology. Additionally, the expandable screen is being developed in other materials so that it will have capability to maintain integrity in more corrosive environments.
The authors wish to thank the management of Halliburton Energy Services Inc. and Shell Exploration & Production Co. for encouragement and support that resulted in successful development of this technology and for permission and encouragement to write this paper.