Recent Applications of Coiled Tubing in Remedial Wellwork at Prudhoe Bay

Abstract

The vast number of wells and unique operating conditions in Alaska's Prudhoe Bay field have presented many opportunities for those involved in remedial wellwork. Among the technologies that have either been pioneered, tested, or applied there, coiled tubing (CT) ranks as one of the most long lasting and widely used. This paper highlights the more recent applications of CT in the field. The paper begins with a brief overview of the Prudhoe Bay Unit's (PBU) CT wellwork program and then follows with discussions on eight CT applications that have been developed or expanded in the last two years. Some are new technology and others are old techniques with a new design. Descriptions and procedures ate given for each in addition to performance results thus far. Introduction The Prudhoe Bay Field contains approximately 1,200 wells which produce over 900,000 barrels of oil per day. Along with this large oil rate, 1.2 million barrels of water and 7.5 billion cubic feet of gas are produced each day. As water processing costs are very high and gas is currently not marketed from the North Slope, the search for reliable water and gas shut-off techniques is never ending. In the continual effort to optimize oil production, PBU wellwork has become a major program. Many tools and technologies have been used over the years in the program, but CT has risen to be one of the most significant pieces of it because of its versatility, capabilities, and cost effectiveness. Typical CT remedial operations cost 5% to 15% of conventional rig options. The large wellwork program and its diverse challenges have provided countless opportunities for CT technology. Many of these advancements have been presented in past papers. As the field ages, wellwork becomes more and more challenging which requires continual improvement in technology to keep pace. This paper highlights the most recent advancements and applications of CT in remedial work. CT Wellwork Program The CT program on the North Slope has grown to be one of the largest in the world. Between the two operators of the nine fields there, 8 coiled tubing units (CTU) are contracted to run on a near daily basis. Two service companies maintain and operate these units and provide critical expertise. In PBU alone, over 1000 CTU operating days are spent on some 600 wellwork jobs striving to keep wells operating efficiently and oil production at a maximum. Applications. There are many applications of CT in the wellwork program at PBU. They range from simple nitrogen lifts to complex remedial completions. Below are the major categories of applications and many of the associated jobs performed. Reservoir Surveillance - Memory surveys and CT electric line logs of all types Capacity Sustainment - Stimulations, perforating, fill clean-outs, nitrogen lifts. Gas & Water Shut-offs - Cement and chemical squeezes, mechanical and inflatable plugs, mechanical straddles. Injection Control - Profile modifications with cement, chemicals, and mechanical devices. Mechanical Repairs - Tubing patches & straddles, cement packer repairs, liner repairs, etc. Miscellaneous - Fishing, ECP's, velocity strings, etc. Prior to the technological advancements of CT, many of these jobs could not have been performed in certain wells or would have been left for a rig workover (RWO). Now, these jobs are often routine events due to the ever expanding use of CT. Technologies. With the variety of CT wellwork being performed naturally comes a variety of associated technologies. Some of the more prominent ones that are advancing the applications of CT are: P. 47

A Review of Recent Developments in Nanomaterial Agents for Water Shutoff in Hydrocarbon Wells

“…Each method is effective in shutting off only specific water paths, and they could be classified into two types: Mechanical methods involve placing a tool of high mechanical strength or cement into the wellbore to shut off the unwanted water source. The mechanical tools involve retrievable and straddle packers, − plugs, tubing patches, and squeeze cementing. − They are preferred for treating near wellbore problems such as channels behind casing or casing and tubing leaks. The advantage of the mechanical methods is that the effect will appear in a short time and is relatively inexpensive compared to other solutions. , However, they are not feasible for treating reservoir-related sources such as fractures or high permeability zones .…”

Frictional Pressure Losses of Fluids Flowing in Circular Conduits: A Review

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“…Flow regime, mainly laminar or turbulent, is a major parameter that affects friction factor. In the treatment of flow of non-Newtonian fluids, Metzner and Reed (1955) defined the generalized Reynolds number on the basis of the power-law model and published a set of critical values to determine the onset of turbulence. In 1883, Osborne Reynolds published and developed what is known as Reynolds number, N Re .…”

Coiled Tubing Deployed Gas and Water Shutoffs in Alaska Utilizing a Polymer Gel and Microfine Cement

“…Through the late 1980s and 1990s there was an active gas and water shut off program wherein several hundreds of coiled tubing cement squeeze jobs were performed. With many candidate wells, there was a continuous evolution in job design and execution techniques over the years (Hornbrook and Mason 1989;Loveland and Bond 1996). Gas and water shut off treatments involving polymer gels alone were also performed, but the long term profile modifications desired were only achieved on a few jobs; typical lives were on the order of 9 months for gels alone (Loveland and Bond 1996).…”

“…With many candidate wells, there was a continuous evolution in job design and execution techniques over the years (Hornbrook and Mason 1989;Loveland and Bond 1996). Gas and water shut off treatments involving polymer gels alone were also performed, but the long term profile modifications desired were only achieved on a few jobs; typical lives were on the order of 9 months for gels alone (Loveland and Bond 1996). Several combination polymer gel and Class G gas shut off cement squeezes were also performed throughout the later 1990s with relatively good results noted, particularly for second or third squeezes of failed cement squeezes that were initially performed with Class G cement only (Lai et al 1999).…”