An Efficient Horizontal Open Hole Multi-Stage Fracturing and Completion System
- Rocky Allen Seale (Packers Plus Energy Services)
- Document ID
- Society of Petroleum Engineers
- International Oil Conference and Exhibition in Mexico, 27-30 June, Veracruz, Mexico
- Publication Date
- Document Type
- Conference Paper
- 2007. Society of Petroleum Engineers
- 2.5.4 Multistage Fracturing, 1.14 Casing and Cementing, 2.5.2 Fracturing Materials (Fluids, Proppant), 5.1.2 Faults and Fracture Characterisation, 5.8.7 Carbonate Reservoir, 2.4.3 Sand/Solids Control, 2.5.3 Fracturing Equipment, 2.2.2 Perforating, 5.8.2 Shale Gas, 2 Well Completion, 1.8 Formation Damage, 4.2.3 Materials and Corrosion, 4.1.2 Separation and Treating, 1.6.6 Directional Drilling, 5.8.6 Naturally Fractured Reservoir, 1.6 Drilling Operations, 1.4.3 Torque and drag analysis, 3 Production and Well Operations
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Over the last two decades many developments have enabled accelerated growth in horizontal drilling. Drilling technologies have pioneered these advancements, with current technology capable of drilling thousands of feet through a thinly bedded hydrocarbon reservoir. Completion advancements designed for extended horizontal wellbores have also advanced, albeit at a slower pace. Initially horizontal drilling was limited to naturally fractured reservoirs with simple open hole or slotted liner completions. This was due primarily to the ability of the reservoir to flow economically without the need for stimulation. Reservoirs requiring stimulation were initially not candidates for horizontal drilling. Developments in completion technology specific for horizontal wells have broadened the reservoirs where horizontal wells can be effectively stimulated.
When drilling a horizontal well, there are two completion options. First, the horizontal can be completed open hole, or with slotted/perforated liner. Effective stimulation along the horizontal wellbore is impossible. The second completion system 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 down of the stimulation equipment are 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 a new open hole completion system run as part of the production liner, does not require cementing and provides mechanical diversion at specified intervals, thus allowing fracturing and stimulations to be effectively pumped to their targeted zone. Details of the engineering design and testing will be specified, with 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.
While horizontal drilling has progressed over the last decade to become the field development method of choice in many cases, there have been certain limiting technologies on the completion of horizontal wells that have proven to slow that growth. This is primarily the ability to effectively stimulate or fracture different intervals of the horizontal wellbore, particularly in reservoirs that were not naturally fractured. The use of limited entry and bullheading techniques provided little if any benefit compared to vertical wells. Post production analysis on the deliverability of horizontal wells in reservoirs such as matrix, heterogeneous and non-conventional formations showed a direct correlation to the completion and stimulation methods employed and their shortcomings in horizontal applications. Thus, the additional economics required to drill a horizontal well was not justified by the equal to or slightly better production results compared to vertical wells.
Horizontal completions where the wellbore is cased and cemented, effective stimulation techniques were addressed some years back by limited entry techniques and then later by the use of composite bridge plugs set on coiled tubing (CT), followed by perforating and then stimulating the well. The bridge plug provides the mechanical diversion in the liner to effectively stimulate each selected zone. This process is then repeated for the number of stimulations desired for the horizontal wellbore. After all the stages have been completed, CT is used to drill out the composite bridge plugs and establish access along the horizontal.1 Although effective, the inherent cost of multiple interventions with CT, perforating guns and deployment of fracturing equipment needed for each stage are extremely high, not to mention very inefficient and time consuming. This coupled with the associated mechanical risks often does not allow for the optimum number of fractures to be placed along a given horizontal interval. Production using this method can also be limiting, as cementing the wellbore closes many of the natural fractures and fissures that would otherwise contribute to overall production.
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