Successful Deployment of Multistage Fracturing Systems in Multilayered Tight Gas Carbonate Formations in Saudi Arabia

Authors: Hasan Hussein Al-Jubran, SPE, Saudi Aramco, Stuart Wilson, SPE, Schlumberger, Bryan Johnston, SPE, Packers Plus

Publication: 2010 SPE Deep Gas Conference and Exhibition, 24-26 January 2010, Manama, Bahrain. SPE 130894

Summary: Horizontal wellbores have enabled significant increases in productive zone contact areas. However, even with these increased contact areas, the expected long-term production increases were not initially realized with conventional stimulation techniques. Multistage fracturing systems have resulted in impressive long-term production improvements, but the deployment of these assemblies into deep and long reach horizontal wells was initially problematic. After the original difficulties were encountered, modifications were made to the well preparation and assembly running procedures which resulted in the recent successful deployment of several multistage fracturing systems into long reach horizontal wells in the Khuff formation in Saudi Arabia. This paper will discuss several factors impacting deployment in these conditions including:

• Construction of the wellbore
• Deploying through multiple layers with varying reservoir pressures
• Preparation of the wellbore
• Running in hole techniques and procedures

With the implementation of these well preparation and deployment techniques, several multistage fracturing assemblies have been successfully installed allowing proper placement of multiple fracturing jobs, which have in turn resulted in continued production improvements from tight gas formations.

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Multi-Stage Acid Stimulation Improves Production Values in Carbonate Formations in Western Canada

Authors: Dan Baumgarten, SPE, Breaker Energy Ltd., Doug Bobrosky, SPE, Packers Plus Energy Services

Publication: 2009 SPE Saudi Arabia Section Technical Symposium and Exhibition, 09–11 May 2009, Al-Khobar, Saudi Arabia. SPE 126058.

Summary: Over the past few years, a new multi-stage, multi-jet fracturing technology has improved the acid fracturing of the Wabamun formation located in south central Alberta..

The Crossfield member of the formation, found in the Swallwell field, has a large original oil and gas reservoir with low recovery factors to date of 2.4% for oil and 5.2% for natural gas. A 1% increase in recovery factors would yield an additional 875,000 bbls and 851,000 mcf of gas.

Use of multiple mechanical isolation points in the new technology has demonstrated average initial production increases of 77 to 102% and final production increases of 12 to 28% compared to historical wells. The micro to very fine crystalline dolomite of the Crossfield member has average permeability ranges from 0.1 and 0.3 mD; therefore, acid stimulation is required in order to economically extract the resource.

This paper will discuss the planning and design processes that led to the implementation of the multi-stage, multi-jet technology. It will outline the lessons learned during deployment of the completion, and will highlight the stimulation treatment execution and post-stimulation results. The text will detail examples from the case studies and will outline the benefits of this technology.

Multiple Tranverse Fracturing in Open Hole Allows Development of a Low Permeabiliy Reservoir in the Foukanda Field, Offshore Congo

Authors: Alberto Casero - SPE, ENI US; Loris Tealdi - SPE, ENI Congo; Roberto Luis Ceccarelli - SPE, ENI E&P; Antonio Ciuca - SPE, ENI E&P; Giamberardino Pace - SPE, ENI Congo; Brad Malone – SPE, Schlumberger; Jim Athans - SPE, Packers Plus Energy Services

Publication: SPE Hydraulic Fracturing Technology Conference held in The Woodlands, Texas, USA, 19–21 January 2009. SPE 119140

Summary: During the past decade, multiple transverse fracturing in horizontal wells has been applied so successfully in onshore low-permeability reservoirs that it is becoming the standard completion practice in many areas.

The reasons for the success of this technique vary, but the two main reasons are related to the undisputed effectiveness of hydraulic fracturing as a production enhancement technique and the relatively low cost of pumping services in onshore areas. Success and industry eagerness for process/cost optimization have contributed to many technological improvements in the multistage completion process allowing sequentially executing several fracturing treatments in a single pumping operation.

Nevertheless, the high direct and indirect costs and the risks associated with offshore operations have traditionally been limiting factors in spreading this technology to offshore applications. Sometimes, the misplaced perception of hydraulic fracturing as risky and costly operation prevented rather than encouraged its application in marginal offshore oilfields.

This study documents the successful effort of taking these techniques to the offshore environment. Transverse fracturing with multistage completion concept— with properly engineered design of well trajectory—can make the difference between the economic success or failure in the field development of low-permeability reservoirs.

The multilayer Foukanda field, located 52km offshore from Pointe Noire, Congo, has a low permeability and virgin target that was considered noncommercial after discouraging results of two wells. Based on the production results of three cased-hole wells in an analogous field where multiple propped fracturing was applied, the operator decided to drill an open-hole horizontal well that was to be multi-fractured. The initial 90 days average production of this Foukanda well was more than 2500bbl/day. This production rate was double the normal rate and opened a wide range of further developments both in Foukanda and in other analogue fields in the offshore Congo.

Successful Case History of a Novel Open-Hole Horizontal Well Completion in Saudi Arabia

Authors: K.M. Al-Naimi, SPE, B.O. Lee, SPE, S.M. Shourbagi, SPE, Saudi Aramco, S.K. Kelkar, SPE, M. Shaheen, SPE, Schlumberger, B. Johnston, SPE, Packers Plus Energy Services

Publication: SPE Asia Pacific Oil & Gas Conference & Exhibition, 20-22 October, 2008, Perth, Australia - SPE 114961

Summary: Horizontal completion technology has progressed dramatically over the last six years, with the latest technical barriers being eclipsed with open-hole technology. These completions have allowed multiple zones to be fractured and the benefits of utilizing open-hole horizontal completion technology have been well documented. The efficiencies and benefits of utilizing open-hole completion with mechanical isolation, has led to the operational benefits of multiple fracturing operations being pumped in one continuous operation equating to time savings, more efficient fractures, faster cleanup and less safety hazards. Conventional methods of cementing a liner in place, perforating, fracturing and repeating the process for the number of stages required can be very time consuming with the added expense of removing the frac plugs with coiled tubing after the operations have been completed.

When drilling a horizontal well, there are two preferred completion options. First, the horizontal section can be completed open-hole or with slotted/perforated liner. In these completions effective stimulation along the horizontal wellbore is almost impossible. The second completion system, cased/perforated liner, requires cementing the production liner and running multiple isolation systems to effectively treat different sections of the wellbore. Multiple coiled tubing trips and multiple rig-up and rig-down of the stimulation equipment is required. These multi-stage horizontal completions take weeks to complete at high costs and elevated risks. Ultimately, the high completion costs or the lack of production due to ineffective stimulation make many reservoirs uneconomical to exploit.

This paper will discuss the new completion designed specifically for open-hole fracturing of both sandstone and carbonate reservoirs. This innovated, field proven system greatly increases the effectiveness of fracturing operations by segmenting the lateral and producing mechanical isolation points in the wellbore using the high performance open-hole packers. The systemis run as part of an uncemented liner and spaced out based on the required number of stages. Once in place the packers are hydraulically set and fracturing treatments are pumped in separate stages but as a single continuous operation. By eliminating cementing requirements, natural fractures are undamaged and easily stimulated during pumping operations.

Successful Deployment of Innovative Completion Technology Designed for Multi-Stage Fracturing Treatments in Horizontal Producers Achieved Significant Rate Increase in Saudi Arabia

Authors: J.R. Solares, SPE, C.A. Franco Giraldo, SPE, H.Al-Marri, SPE, H. Al-Hussain, SPE, N. Abualhamayel, SPE, Saudi Aramco, Venkateshwaran Ramanathan, SPE, O.A. Ishteiwy, SPE, Schlumberger, and Bryan Johnson, SPE, Packers Plus

Publication: SPE Annual Technical Conference and Exhibition, 21-24 September 2008, Denver, Colorado, USA SPE114766

Summary: One of the key strategies in Saudi Aramco’s optimum gas development project includes drilling single and multilateral horizontal wells designed to achieve maximum reservoir contact to maximize productivity. This strategy has proven very successful over the past few years as the majority of horizontal gas producers have yielded excellent results, with open-hole completions in particular. Consequently, most of the planned future wells will be drilled as open-hole horizontal completions.

However, due to the complex nature of the Khuff reservoir some wells have experienced complications during the drilling phase, encountering unexpected reservoir challenges, and hence not meeting production targets. These wells require stimulation to regain their productivity, but the available choices to achieve effective stimulation in horizontal open-hole completions have traditionally been limited at best. Previous stimulation attempts with coiled tubing have yielded modest improvements mainly due to the difficulty in accessing the long, deep, and high pressure/temperature zones requiring treatment. Bullheading treatments at high injection rates have also yielded similar modest well productivity enhancement. Consequently, Saudi Aramco field tested an innovative new completion technology that provided the ability to selectively fracture stimulate multiple zones along the horizontal section, yielding excellent and highly promising results which compared favorably with the performance of nonstimulated offset wells.

Utilizing Modern Frac Baffles Improves Completion Efficiencies

Authors: Michael Arispe, SPE, and Randy Mueller, SPE, Anadarko Petroleum; Chris Meaux, SPE, and Todd Green, SPE, BJ Services; and Daniel Rojas, SPE, Packers Plus

Publication: SPE Annual Technical Conference and Exhibition, 21-24 September 2008, Denver, Colorado, USA SPE116232

Summary: As hydrocarbon production costs rise, the need for greater completion and production efficiency is becoming increasingly important. The Haley Field in the Delaware Basin of West Texas has begun utilizing frac baffles in order to improve the overall efficiency of the multi-stage completion process. The frac baffles, which are strategically placed within the casing string, allow for zonal isolation by means of dropping a frac ball that seats on the frac baffle at the specified depth. The isolated zone is then ready to be perforated and fractured.

The process of utilizing frac baffles has proven to be more efficient compared to the traditional method of setting composite bridge plugs for zonal isolation. First, the need for wireline is reduced because there is no need to set composite bridge plugs. Additionally, the challenges experienced with setting and milling the composite bridges plugs are completely eliminated. Finally, the processes of perforating, stimulating, and coiled tubing milling have been dramatically improved.

In particular, coiled tubing milling of the frac baffles / balls has improved in the areas of milling speed, coiled tubing cycling, and circulation of milled particles returned. Most important, is the significant operational time savings, which allows the well to be brought on production faster.

Successful Multistage Horizontal Well Fracturing in the Deep Gas Reservoirs of Saudi Arabia: Field Testing of a Promising Innovative New Completion Technology

Authors: J.R. Solares, SPE, C.A. Franco, SPE, H.M. Al-Marri, SPE, and H.A. Al-Jubran, SPE, Saudi Aramco; Venkateshwaran Ramanathan, SPE, and Shri Kelkar, SPE, Schlumberger; and Bryan Johnston, SPE, Packers Plus

Publication: CIPC/SPE Gas Technology Symposium 2008 Joint Conference, 16-19 June 2008, Calgary, Alberta, Canada. SPE114768

Summary: One of the key strategies in Saudi Aramco’s optimum gas development project is drilling single and multilateral wells to achieve maximum reservoir contact to maximize well productivity. This strategy has proven very successful over the past few years as the majority of the horizontal gas producers have yielded excellent results, with open-hole completions in particular. Consequently, most of the planned future wells will be drilled as open-hole horizontal completions.
Nonetheless, due to the highly complex nature of the Khuff carbonate reservoir some wells have experienced complications during the drilling phase and encountered unexpected reservoir challenges which has kept them from achieving their production targets. These wells require stimulation to regain their productivity, but the available choices to achieve effective stimulation in horizontal open hole completions have traditionally been limited at best. Previous stimulation attempts with coiled tubing have yielded modest improvements mainly due to difficulty in accessing the long, deep and high pressure/temperature zones requiring treatment. Bullhead treatments at high injection rates have also yielded similar modest well productivity enhancements, because of the inability to achieve effective diversion. Consequently, Saudi Aramco field tested an innovative new completion technology that provided the ability to selectively fracture stimulate multiple zones along the horizontal section. Field trials have yielded excellent and highly promising results, which compared favorably with the performance of non-stimulated offset wells.

Optimizing Horizontal Completions in the Cleveland Tight Gas Sand

Authors: M.L. Samuelson, SPE, T. Akinwande, SPE, and R. Connell, SPE, Schlumberger; R. Grossman, SPE, Panther Energy; and B. Strickland, Packers Plus

Publication: CIPC/SPE Gas Technology Symposium 2008 Joint Conference, 16-19 June 2008, Calgary, Alberta, Canada. SPE 113487

Summary: This paper describes an efficient multistage horizontal openhole completion technique as an alternative to conventional openhole or cemented and perforated lateral completions. The application focuses on openhole (OH) completions in the Cleveland tight gas sand of the Texas panhandle. Horizontal wells have been drilled extensively in this low permeability gas reservoir to enhance productivity.(5) While the increased contact area offers a potential for enhancing well productivity and overall well economics, additional stimulation is usually required. Conventional OH or cemented and perforated completion alternatives have had various operational and logistic issues that have minimized efficiency and production impact. The system applied involves the use of a series of mechanical openhole packers deployed on the production liner with a frac port located between each set of packers and a process of subsequent multistage stimulation of the entire interval. The multistage OH completions have resulted in better connection to the reservoir compared to conventional cased-hole staged completions. Significantly increased completion efficiencies have been realized in all areas of the Cleveland tight gas sand, resulting in reduced completion costs and reduced overall completion timeframes.

Effective Open Hole Horizontal Completion System for Multistage Fracturing and Stimulation

Authors: R. Seale, SPE, Packers Plus Energy Services, J. Athans, SPE, Packers Plus Energy Services

Publication: SPE Tight Gas Completions Conference, 9-11 June 2008, San Antonio, Texas, USA. SPE114880

Summary: This paper describes an efficient multistage horizontal openhole (OH) completion technique as an alternative to conventional openhole or cemented and perforated lateral completions. The application focuses on OH completions in the Edwards Lime of South Texas. Horizontal wells have been drilled extensively in this deep high temperature gas field. This paper will detail the new horizontal completion system run as part of the production liner, which does not require cementing and provides mechanical diversion at specified intervals, so fracturing and stimulations can be pumped effectively to their targeted zone. Details of the engineering design and testing will be specified, with extensive elaboration on the applications and case histories were these systems have been successfully deployed. The case histories will detail the operational efficiencies of the system in conjunction with the enhanced production realized.

Application of a Novel Open-Hole Horizontal Well Completion in Saudi Arabia

Authors: K. M. Al-Naimi, SPE, B. O. Lee, SPE, K. M. Bartko, Saudi Aramco, S. K. Kelkar, SPE, M. Shaheen, SPE, Z. Al-Jalal, Schlumberger, and B. Johnston, SPE, Packers Plus Energy Services

Publication: SPE Indian Oil and Gas Technical Conference and Exhibition, 4-6 March 2008, Mumbai, India. SPE113553

Summary: Horizontal completion technology has progressed dramatically over the last six years, with the latest technical barriers being eclipsed with open-hole technology. These completions have allowed multiple zones to be fractured and the benefits of utilizing open-hole horizontal completion technology have been well documented. The efficiencies and benefits of utilizing open-hole completion with mechanical isolation, has lead to the operational benefits of multiple fracturing operations being pumped in one continuous operation equating to time savings, more efficient fractures, faster cleanup and less safety hazards. Conventional methods of cementing a liner in place, perforating, fracturing and repeating the process for the number of stages required can be very time consuming with added expense of removing the frac plugs with coiled tubing after the operations have been completed.

When drilling a horizontal well, there are two preferred completion options. First, the horizontal section can be completed open-hole or with slotted/preperforated liner. In these completions effective stimulation along the horizontal wellbore is almost impossible. The second completion system, cased/perforated liner, requires cementing the production liner and running multiple isolation systems to effectively treat different sections of the wellbore. Multiple coiled tubing trips and multiple rig-up and rig-down of the stimulation equipment is required. These multi-stage horizontal completions take weeks to complete at high costs and elevated risks. Ultimately, the high completion costs or the lack of production due to ineffective stimulation make many reservoirs uneconomical to exploit.

Continuous Pumping, Multistage, Hydraulic Fracturing in Kitina Field, Offshore Congo, West Africa

Authors: Alberto Casero – SPE, Eni E&P; Giamberardino Pace – SPE, Eni E&P; Brad Malone – SPE, Schlumberger; Francois Cantaloube – SPE, Schlumberger; Loris Tealdi – SPE, Eni Congo; Henri Malonga – SPE, Eni Congo; Rocky Seale – SPE, Packers Plus Energy Services.

Publication: 2008 SPE International Symposium and Exhibition on Formation Damage Control held in Lafayette, Louisiana, U.S.A., 13–15 February 2008. SPE112442

Summary: During April to June of 2007, eight hydraulic propped fractures were placed in three re-completed, cased-hole wells in the Kitina Field offshore from Pointe Noire, Congo, with very encouraging production increases. During the first 90 days of post fracturing production, a production increase of 200% was achieved. This paper will discuss the steps that were taken to place these propped fractures from an ocean going tender barge using skid equipment and recommendations for the future applications of this stimulation technique.

*The papers listed above were selected for presentation by an Society of Petroleum Engineers (SPE) program committee following review of information contained in an abstract submitted by the authors. The abstracts listed are not more than 300 words and are the copyright of SPE.