Openhole gravel packing - Openhole completions provide another opportunity for sand control. Many engineers do not routinely think of performing an openhole completion when confronted with selecting a completion. This is true probably because cased- hole completions are so widely accepted and because they are not familiar with selection criteria and procedures. Openhole completions can provide excellent, high- productivity completions, but they must be applied under the right reservoir conditions. They avoid the difficulties and concerns of perforation packing and reduce the gravel- placement operations to the relatively simple task of packing the screen/openhole annulus.
Openhole gravel packing. completed maintaining borehole stability in the completion interval. Wells where cased-hole completions are. the open hole.
Open-hole completion system enables multi-stage fracturing and stimulation along horizontal wellbores. open hole wellbores allows zones to be. OPEN HOLE COMPLETION SYSTEMS KENTUCKY OIL & GAS ASSOCIATION 2014 Ryan Henderson Technical Sales Director Peak Completions.
Punawai-1 Well Project Drilling & Completion Design June2012 Page 3 1. Introduction Punawai-1 is a vertical exploration well to be drilled by a joint venture between. Well completion. From AAPG Wiki. Jump to: navigation. In a typical open hole completion, casing is set prior to drilling into the producing interval. Open hole completion. This designation refers to a range of completions where no casing or liner is cemented in place across the production zone. Technical Paper: Challenging Horizontal Open Hole Completion in Carbonates: A Case History on Mechanical Isolation and Selective Stimulation in Campos Basin, Brazil. The Breakdown Pressure Calculating Model for Open Hole Completion The Open Fuels & Energy Science Journal, 2014, Volume 7 13 (3) Ignore the influence of physical and.
Because openhole gravel packs have no perforation tunnels, formation fluids can converge toward and through the gravel pack radically from 3. В°, eliminating the high pressure drop associated with linear flow through perforation tunnels.
The reduced pressure drop through an openhole gravel pack virtually guarantees that it will be more productive than a cased- hole gravel pack in the same formation, provided they are executed properly. Theoretical pressure drops.
Fig. 1 illustrates the theoretical pressure drops experienced in openhole and cased- hole gravel packs. It reveals that openhole gravel packs result in virtually no additional pressure drop as the formation fluids converge at the wellbore. Fig. 1вЂ”Comparison of pressure drawdowns for cased- and openhole gravel packs.Guidelines for selecting openhole gravel pack candidates. Despite their potential for creating high- productivity wells, openhole gravel packs are not suitable for all reservoirs and formations. One disadvantage of the openhole completion (including openhole gravel packs) is the inability to always isolate unwanted water and/or gas production.
Unlike cased- hole completions that can be precisely and selectively perforated in the zones of interest, openhole completions sometimes offer less control over fluids (water, oil, and gas) exposed to the wellbore. In a cased- hole, remedial operations such as squeeze cementing, plugbacks, or straddle packoffs to isolate unwanted fluid production are can be carried out with a reasonably good chance of success with little to no planning. Such remedial operations in an openhole well (with the exception of a plugback) require additional planning to isolate undesirable fluids.
With this in mind, openhole completions are best suited for thick reservoir sands rather than multiple sand reservoirs where there is water and/or gas to contend with. Maintaining borehole stability during drilling and completion is an essential requirement for openhole gravel packs. Concern over the lack of borehole stability is a primary reason that openhole gravel packs are not used more often in unconsolidated, dilatant formations. Unstable boreholes make running of the gravel- pack assembly difficult and may prevent proper gravel placement if the formation flows in around the screen. Fortunately, state- of- the- art drill- in fluids are usually effective in maintaining borehole stability while performing a horizontal completion in dilatant- type formations.
Openhole gravel packs should be avoided in formations with several sand and shale laminations if the shales are prone to uncontrollable eroding and/or sloughing. During gravel placement, the shale can intermix with the gravel- pack sand, resulting in reduced gravel permeability and impaired well performance. Again, proper drill- in fluid selection can alleviate some of the problems associated with laminated sand and shale formations. Openhole gravel- pack candidates include. Formations where cased- hole gravel packing has unacceptable productivity. Wells where increased productivity is required.
Reservoirs where long, sustained single- phase hydrocarbon flow is anticipated. Situations where workovers for isolating gas or water cannot be accomplished. Wells where high water/oil or gas/oil ratios can be tolerated. Reservoirs with single uniform sands (avoid multiple sands interspersed with troublesome shale layers or water sands).
Formations that can be drilled and completed maintaining borehole stability in the completion interval. Wells where cased- hole completions are significantly more expensive (i. Top set openhole gravel pack. The most common type of openhole completion is referred to as вЂњtop set,вЂќ which is illustrated in Fig. While this figure shows a vertical completion, this discussion is also pertinent to openhole horizontal wells. In this completion, the production casing is set at the top of the completion interval to isolate overlying strata.
Once the casing is cemented, the following steps are undertaken. Productive formation is drilled to total depth. Hole is cleaned and displaced. Gravel pack is installed. Fig. 2вЂ”Top set openhole gravel- pack completion (courtesy of Baker Oil Tools).
Critical issues. Critical issues in top- set openhole gravel packs include. Selecting the casing seat. Drilling the open hole. Underreaming, if necessary. Cleaning the hole and gravel packing.
Selecting the casing seat. Selecting the casing seat at the proper depth can have a significant impact on the success and cost of an openhole completion.
Normally, the casing should be set at the top of the reservoir, just barely into the productive interval. If the overlying formation is an unstable or sloughing (heaving) shale, failure to isolate the shale behind casing may cause problems and delays throughout the remainder of the completion.
Well logs should be run to ensure that all offending strata have been penetrated and will be cased before running the casing. In some instances, several logging runs may be required as the well is deepened to determine exactly when the casing should be run. In the case of logging while drilling, the casing point can be easily picked without multiple logging runs. Alternatively, the well can be drilled to total depth and logged to determine the appropriate casing depth. Then a sand plug can be placed across the productive interval before cementing the casing. Drilling the open hole. Several options are available for drilling the openhole completion interval.
How this is performed and the type of fluids used depend on the mineral and fluid content of the formation (i. Another factor is whether to enlarge the hole by underreaming. The fluid used for drilling the open hole is critical to the success of the completion. The general requirements of an ideal drill- in (or underreaming) fluid, which apply to any openhole completion and are not specific to gravel packs, are. Compatibility with the reservoir rock and fluids (nondamaging)Good suspension properties. Low friction loss. Low fluid loss. Easily controlled density.
Ready availability. Low cost. Ease of mixing and handling.
Nontoxicity. Thin friable filter cakes with low breakout pressure. While most fluids do not have all of these properties, some, such as calcium carbonate brine fluids, have performed well as drill- in and underreaming fluids. The critical issue is that the drill- in fluid should do minimal irreversible damage to the face of the formation. The solid- laden fluids should quickly form a filter cake to minimize filtrate losses. The filter cake should be easily removable before or after gravel packing.
The ease with which it is removed is reflected in a low breakout pressure. Breakout pressure is reached when drawdown pressure, required to initiate production after the formation, has been mudded off with the drill- in fluid. In rare cases, clear brines have been acceptable as nondamaging drill- in fluids. If the open hole is to be underreamed, standard drilling mud may be used as a drill- in fluid, provided that the underreaming operation, using calcium carbonate brine- based systems, removes the mud- invaded, damaged portion of the formation. Underreaming. Underreaming is the operation of enlarging the hole size below the casing shoe.
One reason for underreaming an open hole is to remove damage present in the pilot hole. Underreaming may be unnecessary if the pilot hole is drilled with a nondamaging fluid. The larger- diameter hole also enhances the well productivity slightly, but in most cases, this is insignificant. Underreaming may be performed simply to provide greater clearance between the screen and the open hole.
In any event, underreaming should be performed with a nondamaging fluid that keeps the hole stable. Traditional drilling muds should be used only as a last alternative, and damage- removal treatments should be planned before placing the well on production if these muds are used. Underreaming is usually more of an annoyance than an incremental time, cost, or productivity issue because a cased- hole completion also requires changing over to a clean fluid before perforating. Perforating, of course, is unnecessary. Underreaming and perforating usually offset each other in incremental costs. In the event that running a liner across the completion interval at a later date is an option to isolate unwanted fluids, underreaming probably should be avoided. The cement sheath in an underreamed hole will be much thicker than normal and will interfere with effective perforating or make perforating operations more difficult.
The difficulties are that perforating, or ineffective perforations, will adversely affect gravel packing and, subsequently, will restrict well productivity. Hole cleaning. The hole may contain solids that need to be removed. These solids can be any of the following.
Drill- in fluids. Drill solids. Gravel- pack sand. The importance of cleaning the hole and the filter cake is shown in Fig. This bar graph is based on field data collected from 1.
This relationship is not too surprising, but what is often overlooked is that once a well is damaged, subsequent acid treatments increase productivity but will not yield an undamaged well. Before running the screen in the hole and gravel packing, it is necessary to. Remove the drill- in fluid.
Drill solids from the hole.
Well completion - AAPG Wiki. Purpose of well completions. The purposes of a well completion are to. Connect the reservoir to the surface so that fluids can be produced from or injected into the reservoir. Provide a conduit for well stimulation treatments. Isolate the producing reservoir from other zones.
Protect the integrity of the reservoir, especially in unconsolidated formations. Provide a conduit to measure the changes in flow rate and pressure needed to run a well test. The wellbore provides the only path from the surface to the reservoir. To a large extent, the successful production and depletion of a reservoir depends upon the successful completion and workover operations applied to a well. In most companies, the production engineer designs and supervises all completion and workover operations. Types of completions. Completions can be divided into three categories: open hole completions, liner completions, and perforated casing completions.
In most wells, conventional single perforated casing completions are used; however, multiple, alternate, or slim hole completions may be used under certain conditions. The choice of completion type should be closely coordinated with the development of the reservoir management plan. For example, the size, weight, and grade of the tubular goods will be determined based upon the ultimate use of a wellbore. An injection well may require stronger casing than a production well. Open hole completions. Open hole completions were originally used in the early days of the petroleum industry when most wells were drilled with cable tools. Normally, casing was run as the hole was drilled.
When the formation was penetrated and oil and gas began to flow, drilling ceased and the well was produced as an open hole completion. As rotary rigs began to drill a majority of the wells, it was still common to complete a well using an open hole completion. If the well needed to be stimulated, nitroglycerine was used to rubbleize the formation near the wellbore. Figure 1(a) illustrates a typical wellbore diagram for an open hole completion. Although not common in most areas, open hole completions are still used today in certain situations, such as the horizontal well completions in the Austin Chalk and in the Devonian shales in Appalachia. In a typical open hole completion, casing is set prior to drilling into the producing interval. A nondamaging fluid can then be used to drill into the pay section.
One important disadvantage of an openhole completion is that production casing must be set prior to drilling and logging the reservoir. If for some geological or engineering reason the target formation is not productive, then money has been spent to set casing in a well that may be plugged as a dry hole.
Another disadvantage is the lack of control that occurs when an open hole completion is made. One cannot control the flow of fluids from the reservoir into the wellbore nor the injection profile in an open hole completion. In addition, if the formation is not competent, sloughing zones can cave into the wellbore and restrict flow to the surface.
Liner completions. Liner completions are similar to open hole completions in that casing must be set prior to drilling the producing interval. The advantage of a liner completion is that the drilling fluid system can be changed and a nondamaging fluid used to drill the pay interval. Several types of liner completions are commonly employed in well completions. These include. Screen and liner.
Cemented liner. The slotted liner completion is similar to an open hole completion and has all the major advantages and disadvantages discussed for open hole completions. The only difference is that a slotted liner is hung in the open hole interval to minimize sloughing of the formation into the well bore (Figure 1b). A screen and liner completion is similar to the slotted liner completion in that a screen and liner is set in the open hole section of the wellbore. The difference is that gravel is sometimes placed behind the screen (Figure 2a). The advantages and disadvantages are the same as for open hole completions. The screen and liner completion is used primarily in unconsolidated formations to prevent the movement of formation materials into the wellbore, restricting the flow of reservoir fluids. The cemented liner completion is used when intermediate casing is set in a well prior to reaching total depth (Figure 2b).
Many times intermediate casing is used to isolate zones behind pipe such as low pressured intervals that tend to cause lost circulation problems or to isolate zones such as sloughing shales or salt layers. Intermediate casing is also set in transition zones between normally pressured intervals and geopressured intervals. After the casing is set, the weight or chemistry of the drilling fluid can be changed to continue drilling the well. The cemented liner completion is advantageous because the particular intervals behind the liner can be selectively perforated. This selection will allow one to control both the production and injection of fluids in those intervals. The main disadvantage of a cemented liner is the difficulty encountered in obtaining a good primary cement job across the liner. If a good cement job is obtained, then a cemented liner completion is very similar to a perforated casing completion.
Perforated casing completions. A perforated casing completion, illustrated in Figure 3a, is the most commonly used completion technique today. The main advantage of this type of completion is that the well can be drilled and logged to total depth prior to running and cementing production casing.
By obtaining cores and logs of the potential producing interval, one can estimate the economic value of that wellbore prior to committing funds to complete the well. Another advantage of a perforated casing completion is that it is easier to obtain a good cement job, compared to a liner completion. If the primary cementing job is properly performed, one can selectively produce from and inject into the reservoir and isolate intervals as required. The production of an unconsolidated formation can be accomplished by performing an inside gravel pack. Finally, the perforated casing completion is quite adaptable to multiple completions and alternate completions.
Single completions. Once the decision has been made to either complete a well using an open hole completion, liner completion or perforated casing completion, a decision must be made on how many different intervals will be produced. The most common method is the single completion in which only one interval is produced at a time (Figure 3b). A single completion is simple and results in fewer operating problems and less cost than multiple completions.
Single completions are common on land where the reservoirs are either shallow or very deep. If the formation is very shallow, then drilling costs are minimal and single completions are usually best.
In very deep wells, single completions are preferred because of the complexity and expense involved with a dual or triple completion in reservoirs deeper than 1. Multiple completions. Figure 4 Wellbore diagram of (a) a casing- tubing dual completion and (b) a completion with dual packers and dual tubing strings. Figure 5 Wellbore diagram of a conventional triple completion. In certain cases, multiple completions may provide the best control of reservoir operations. Multiple completions include the tubing- casing dual, dual tubing strings, and the typical triple completion consisting of three tubing strings.
Figures 4 and 5 illustrate these multiple completions. The more complex the completion, the more trouble one can expect in both completion operations and in subsequent workover operations. Multiple completions should be considered only in special situations.
These situations include areas where drilling costs are very high or where the area allocated for drilling wells is at a premium. Such areas include offshore areas, highly populated areas, and remote land locations. The main advantage of multiple completions is that two or more reservoirs can be simultaneously produced from a single wellbore. If all goes properly, the economics of using multiple completions can be attractive; however, operating and workover costs can be quite high. These operational factors must be considered when considering multiple completions.
Alternate completions. Alternate completions are used to allow inexpensive recompletions. Normally, a single interval is completed and produced to abandonment and then, using wireline tools, the lower interval is isolated and the upper interval opened to production (Figure 6). Alternate completions eliminate the need for costly workovers using rigs. It is possible to have a dual well with two alternate completions; however, as the completion gets more complex, more problems will occur. Alternate completions are used in areas where workover costs by conventional methods can be quite high. The most common use of alternate completions is offshore.
Slim hole completions. In certain reservoirs, the economic value of the reserves does not justify the expenditures of normal completion methods. An example of such a reservoir would be a series of thin, small lenticular dry gas intervals. Under certain conditions, the reservoir might not warrant the use of large production casing and tubing to produce the gas. For such reservoirs, slim hole completion techniques might be justified in which small pipe, such as 4- 1/2- in. This small casing serves as the tubing and casing for the wellbore. This completion practice is used to minimize completion costs and should be used only for wells that are expected to have short producing lives and that do not require artificial lift.
Special considerations for producing and injection wells. The completion technique applied to a well depends on whether the well is a producing well or an injection well. For a producing well, the number of different reservoirs that may eventually be produced is significant.