TECHNOLOGY Isolation profile liner helps stabilize problem well bores

Gabdrashit S. Abdrakhmanov
TatNIPIneft
Bugulma, Tatarstan

Rustam Ibatullin
International Neftegaz Consultants
Bugulma, Tatarstan

Brad Robinson, Bill Powell
S.A. Holditch & Associates Inc.
Houston

An expandable full-bore liner can cover long, lost circulation zones to eliminate the need for intermediate casing strings.

This liner has also successfully repaired various casing problems in producing wells.

As drilling depth increases, so does the demand and costs associated with specialized oil field services and equipment, such as cementing in hostile environments and special casing designs. Special casing designs are needed to isolate zones of different pressures and formations (fractured intervals, sloughing shales, etc.) that can cause drilling problems.

In Russia, the costs associated with these special casing and cementing operations can range from 26 to 77% of the total well cost, primarily because of the need for intermediate casing strings. Drilling operations in certain areas of the former Soviet Union have required intermediate casing strings to be set at depths in excess of 13,000 ft.

The TatNIPIneft Institute, which is the largest oil and gas research institute in Tatarstan, has designed and patented an isolation profile liner, which was initially manufactured to eliminate the need for intermediate casing strings because of lost circulation or pressure depleted formations. To date, the liner has been successfully installed in approximately 850 wells throughout Russia.

Installation

The isolation profile liner is constructed from a proprietary alloy that can be expanded from a collapsed state once the tool is run to the proper setting depth. To maintain the full working diameter of the well bore, the driller must underream the hole slightly above, below, and across the problem zone (Fig. 1 (95640 bytes)).

The liner is then expanded into the underreamed portion of the hole by using pump pressure and a specially designed expansion tool. An epoxy material applied to the outside of the profile liner adheres to the borehole wall, thus keeping the liner in place.

Casing design

Eliminating the need for intermediate casing strings reduces the cost and time associated with drilling operations. In addition, it can reduce the borehole diameter and accordingly, the conductor and surface casing diameters in the upper sections of the well, further reducing the overall drilling costs.

For example, the isolation profile liner was installed on the Utyaevskaya No. 53, eliminating the need for about 3,400 ft of 958-in. (245 mm) casing and reducing the conductor and surface casing requirements (Fig. 2 (92515 bytes)a).

In some instances, several liners have been run on wells containing multiple lost circulation zones (Fig. 2 (92515 bytes)b). The profile liner has also been run to isolate cavernous zones found in the Uglenosny and Vereiski formations (Fig. 2 (92515 bytes)c).

The liner has been used in the Tataria, Bashkiria, Udmurtia, Samarskaya, and Orenburgskaya regions of Russia to successfully isolate both fractured and cavernous lost circulation zones. It has been run in a variety of borehole diameters and has eliminated the need for intermediate casing strings ranging in size from 958 in. to 7 in.

Lost circulation zones

Serious lost circulation problems sometimes occur unexpectedly, and in many cases, these problems can jeopardize the completion of a well.

For example, on Well No. 2602, the Orenburgneft Co. encountered a problem zone and was unable to regain circulation using conventional techniques. The company was ready to abandon the hole and redrill the well when the decision was made to set a profile liner. The liner was successfully installed over an 89-ft interval, and drilling operations were resumed (Fig. 2 (92515 bytes)d).

The profile liner can also be installed on the bottom of an existing casing string (Fig. 2 (92515 bytes)e). The Bratsk No. 160 encountered a cavernous lost circulation zone after the 858 in. casing was drilled out. The company had initially decided to abandon the well after conventional lost circulation techniques failed. The cavernous zone was successfully isolated with a 95-ft long profile liner, however, and drilling operations continued to the planned total depth.

Casing repair

The TatNIPIneft Institute has also had great success in restoring production on existing wells with collapsed or split casing strings.

A honing mill is used to expand the internal diameter of the casing, and the profile liner is installed with the same previously described installation process, with only a slight restriction of the internal diameter (Figs. 3a-3b (90019 bytes)).

Figs. 3c-3e (90019 bytes) depict several wells in which casing has been repaired or existing perforations were successfully shut off using the profile liner.

More than 50 wells in several regions of Russia had successful casing repairs with the isolation profile liner. These casing repair applications, in conjunction with elimination of lost circulation in several hundred wells, have proved the isolation profile liner to be an effective, highly reliable solution to many common drilling and completion problems.

Based on these achievements, use of the profile liner has been expanded to additional applications.

Other applications

In some cases, the liner has been successfully installed during the early portions of the well and then subjected to long periods of continuous rotary drilling operations.

For example, the Zaikinskaya No. 2602 well has withstood very severe drilling operations in which the liner remained secure for several weeks, including tripping the drill pipe 79 times (Table 1)(14182 bytes).

Because of a measurement error in Well No. 14124, the profile liner was installed only over the lower portion of the lost circulation zone. A second profile liner was successfully run and sealed above the previously installed liner, completely eliminating the lost circulation problem.

On Well No. 2601, a profile liner, accidentally damaged during drilling operations, was successfully repaired by overlapping a second liner across the damaged section.

The isolation profile liner has also been used to isolate an aquifer across the Aleksinsky formation in the Romashkino field. In this particular application, the liner isolated an abnormally pressured aquifer (0.574 psi/ft pressure gradient) which was flowing into the borehole during drilling operations.

The profile liner has also been used to enhance primary cementing of production casing by isolating producing formations from adjacent aquifers (Fig. 4 (58754 bytes)). Sealing off the water-productive zones helps to minimize the chances for channels behind pipe that could result in excessive water production.

The liner can also be used to protect water-sensitive or cement-sensitive pay zones from severe formation damage resulting from deep cement invasion. This invasion damage is a serious problem in deep, fractured, or vugular carbonate reservoirs where acid treatments are ineffective because of high bottom hole temperatures.

Research is currently being conducted to use the profile liner as a liner hanger in lateral extensions from existing vertical wells.

The biggest advantage of using the profile liner is that the material is easily drillable and can be removed from the original (vertical) well bore, allowing a full working diameter. This ability can have a direct impact on drilling and casing multiple laterals off the original vertical well.

A new, high-capacity manufacturing plant is under construction is Aznakaevo, Tatarstan. The new plant, scheduled to begin operation in 1996, will be able to provide the oil and gas industry with isolation profile liners ranging in size from 51/2 in. to 111/3 in.

The Authors

Gabdrashit S. Abdrakhmanov is the manager of local well casing technology for TatNIPIneft in Bugulma, Tatarstan. In 1964, Abdrakhmanov graduated from the Moscow Petroleum & Gas Institute where he studied oil field development. In 1970, he completed a candidate degree on the prevention of drilling problems. In 1990, he received a PhD for his research in developing the theory and practical application of local well casing. Abdrakhmanov. He has published 217 papers, including two manuals "Drilling of Oil and Gas Wells" and "Drilling Process Control". He holds 27 foreign patents, two of which are American.

Rustam Ibatullin is the chairman and chief executive officer of International Neftegaz Consultants and director of the Tatar Oil Research & Design Institute in Bugulma. Prior to assuming his present responsibilities at TatNIPIneft, Ibatullin was manager of the largest drilling enterprise within the Tatneft Amalgamation. He graduated from the Ufa Petroleum Institute in 1955 as a drilling engineer. In 1965 he was awarded a PhD by IGIRGI. Ibatullin has published more than 150 articles about petroleum technologies and holds 50 patents.

Bradley M. Robinson is vice-president in charge of production engineering for S.A. Holditch & Associates Inc. He has been responsible for several large projects, including an hydraulic fracturing research program for the Gas Research Institute and a fracture stimulation optimization program for several large gas fields in Indonesia. Robinson has been extensively involved in fracture treatment design, post fracture formation evaluation, fracture diagnostics, and field supervision. He previously worked for Marathon Oil Co. in production and reservoir engineering. Robinson has BS and MS degrees in petroleum engineering from Texas A&M University.

W.E. (Bill) Powell is the corporate marketing manager for S.A. Holditch & Associates Inc. in Houston. He is responsible for domestic and international marketing of Holditch petroleum engineering services and software, with special emphasis on developing the commercial software business. He previously worked for Conrad Land Surveying Corp. and was a physics and physical science instructor at Angelo State University in San Angelo, Tex. Powell worked for Schlumberger Well Services as a field engineer, sales engineer, district manager, computer center manager, basin sales manager, and division sales manager. He Joined S.A. Holditch in 1992. Powell has a BS in physics from Lamar University and an MS in physics from Florida State University.