Part II 2 Basic Well Completion Technology.ppt

1、Lesson 2,Basic Well Completion Technology,2.1 Basic Completion Methods,2.2 Completion Procedure,Each drilled wellbore awaiting completion is unique. Even nearby wells drilled to the same reservoir can have different depths, formation characteristics, and hole sizes. It follows, then, that a wide var

2、iety of equipment designs and procedures have been developed to provide safe, efficient conduits from subsurface reservoirs to the surface in different situations. In each case, the ideal completion design minimizes initial completion and operating costs, while providing for the most profitable oper

3、ation of an oil or gas well over its entire life.,Basic Completion Methods,After successfully drilling and evaluating a well, the next decision is whether to complete or abandon it. In abandoning a well, a cement plug (or plugs) is set in the hole, whatever casing can be removed is recovered, and th

4、e drillsite is returned to its original condition. The next step toward completing a well involves the running of the final string of casingthe production string. The manner in which this is done determines the basic completion method and may follow one of several configurations:,水泥塞,井场，井位,生产管柱,Basi

5、c Completion Methods, the openhole completion, the liner completion, the cased and perforated completion,in which the producing formation in not isolated by the casing, which extends only to the top of the producing interval (fig. 2.1a),which is not cemented and not “tied back”to the surface(fig. 2.

6、1b) ;,the cased and perforated completion (fig. 2.lc), which involves cementing the production casing across productive interval and then perforating the casing for production. When a liner is cemented and perfected (fig. 2.1 d) it could be considered a cased and perforated completion.,Basic Complet

7、ion Methods,Figure 2.1 Cross section of basic completion configurations at the formation: openhole completion, slotted liner completion, (d) cased and perforated completions,Figure 2.1 Cross section of basic completion configurations at the formation: (a) openhole completion, (b) slotted liner compl

8、etion, and (c) and (d) cased and perforated completions.,Basic Completion Methods,One of these configurations will be the basis for the completion design, which may incorporate one or multiple strings of tubing and a variety of tubing components to facilitate production from one or multiple zones. A

9、 cased and perforated well with a single tubing string will serve to illustrate the typical completion procedure.,完井设计,Completion Procedure,After the contract casing crew runs the final casing, cementing follows the usual procedure, although stage cementing may be necessary to cement an extremely lo

10、ng string. The production string has been hauled out to the location and the inside diameter checked to make sure that imperfections will not prevent the subsequent running in of tubing and packers after the string is set. Special care must be taken to prevent the possibility of future leaks.,运到，拉到,

11、内径,油管,封隔器,Completion Procedure,If stage cementing is necessary, the bottom section is first cemented in place and then a series of plugs are pumped down the casing to open ports that allow the upper end of the annulus to receive cement. After the cement has set, the inside of the casing must be dril

12、led out and flushed clean of cement and other debris to a depth below that of the proposed completion. It is important that the inside diameter of the production casing be clean and smooth.,柱塞,Completion Procedure,It is also important that the cement form a competent seal between the casing and bore

13、hole over the entire openhole interval. To ensure this, an acoustic cement bond log is sometimes run on electric line to determine if voids exist between casing and hole because cement has bypassed the drilling fluid (fig. 2.2). If the bond is poor in an area, particularly if the area is between pro

14、ductive formations, a cement squeeze will be required. This technique involves selectively perforating the casing and pumping cement into the empty spaces.,井眼,裸眼段,水泥环声波测井,打水泥塞,Completion Procedure,Figure 2.2 Poor cementing job resulting in communication between permeable zones via a channel in the c

15、ement sheath surrounding the casing.,Completion Procedure,Often the cement bond log is run in conjunction with a gamma ray log and a casing collar log. The drilling engineers can correlate this gamma ray log with the logs run earlier during formation logging. This correlation is important because as

16、 we zero in on the targetthe productive formationthe need to locate tools precisely relative to that formation is critical.,By using the correlation log and casing collar log to set packers and perforate, we are assured of precise placement. At this point, many operators move the drilling rig off lo

17、cation and replace it with a less expensive, and often less powerful, completion rig. This gives the operator time to design the rest of the completion, provide for a sales contract, and order equipment.,Completion Procedure,Whichever rig is used, the next step in the completion is to measure the tu

18、bing while running it into the hole. A careful count must be kept of the exact number of tubing joints run into the hole and their total length. With the tubing in the hole, the BOP stack, which is now attached above the tubing head where the tubing will hang, may be tested. The casing may also be p

19、ressure tested, and a filtered completion fluid may be circulated into the well to displace the drilling mud prior to perforating.,Completion Procedure,With the well perforated, it may now be time to stimulate the well by either acidizing or hydraulically fracturing the formation. Acid can be used t

20、o dissolve formation-damaging particles left by the drilling mud or to eat away portions of the rock itself, increasing the size of flow passages. Hydraulic fracturing involves the high-pressure pumping of fluid into the formation to split the rock apart and to increase the flow capacity of tight fo

21、rmations.,Completion Procedure,Normally, the next step is to run and set a completion packer, either incorporated into the tubing string or set independently on electric wireline. The packer is pressure tested to ensure its sealing ability. The tubing must then be “spaced out.” This requires that a

22、length of tubing be removed from the upper end so that it can be “landed” in the tubing head, which is some distance below the rotary table. Once the tubing has been landed in the tubing head, a temporary plug can be set inside the tubing while the BOP stack is removed and the surface flow control e

23、quipment (“Christmas tree”) installed. This plug is then removed through the Christmas tree, and the well is completed.,2.2.1 Perforating,Completion Procedure,2.2.2 Stimulation,2.2.3 Sand Control,Perforating,Jet perforating is the procedure whereby an explosive charge is used to selectively open pas

24、sages to the formation through the casing and cement sheath. This method is the most widely used today, because of its versatility and power.,1,Perforating,Jet perforating guns consist of a carrier with a series of explosive charges linked together by a detonating cord. A variety of gun designs exis

25、t; they vary according to: whether the gun is to be run on an electric conductor line or attached to the bottom of the tubing; whether the gun is to be run through the casing on electric line or tubing, or is to be lowered through the tubing on electric whether the gun is retrievable following deton

26、ation or is expendable (meaning it is destroyed when the gun is fired); the diameter and length of the perforation desired.,2,Perforating,Wider, longer perforations require larger, stronger jet charges, and, accordingly, larger guns to hold them. The charge itself is held in a metal case (fig. 2.4)

27、that is linked to similarly shaped charges by a detonating cord ending in an electric detonator. When the gun is fired, an electric current from the surface sets off the blasting cap detonator, which secondarily ignites the detonating cord leading to the main explosive charges.,3,Perforating,Retriev

28、able hollow carrier guns have cylindrical steel bodies with closed ports opposite each jet charge (fig. 2.6a). Fully expendable guns enclose the charges in a frangible aluminum or ceramic case that disintegrates on firing (Fig. 2.6b), whereas semiexpendable guns consist of wire. or metal strip carri

29、ers that are retrieved after firing (fig. 2.6c). Through-casing and through-tubing guns of these types differ primarily in the diameter of the gun and in the size of the jet charges.,4,Figure 2.6 Perforating charg carriers: (a) cutaway of a bollow cylindrical steel carrier, (b) expendable gun with f

30、rangible aluminum charge cases, and (c) semiexpendable gun with wire strip carrier.,Perforating,The decision about the interval to be perforated is often made by the geologist or by the engineer and geologist responsible for the area in which the well is drilled. Consideration will be given to maxim

31、izing flow rate and minimizing production problems such as produced sand, water coning, or excessive gas production in an oil well. The decision is often made after careful review of the log and core data back at the company office. The geologists input concerning net pay, sidewall core descriptions

32、, and the areal extent of sand intervals can be crucial in determining the best interval to be perforated.,5,Stimulation,With the well perforated, it may now be time to stimulate the well by either acidizing or hydraulically fracturing the formation. Acid can be used to dissolve formation-damaging p

33、articles left by the drilling mud or to eat away portions of the rock itself, increasing the size of flow passages. Hydraulic fracturing involves the high-pressure pumping of fluid into the formation to split the rock apart and to increase the flow capacity of tight formations.,1,Stimulation,Acidizi

34、ng: Successful acidizing involves more than simply pumping acid down the well and allowing it to dissolve part of the formation. The type of acid used, the chemicals added to improve its efficiency, the volumes pumped, and the pumping pressures maintained are dependent on the characteristics of the

35、reservoir rock and fluids and the configuration of the well.,2,Hydrochloric acid (HCI) is the most common chemical used in acidizing. A solution of 15% HCI by weight is most often used in limestone or dolomite formations. In sandstone formations with interstitial clays, particularly in areas such as

36、 the Texas and Louisiana Gulf Coast of the United States, a mixture of 12% HCI and 3% hydrofluoric (HF) acid is often used. Organic acids, such as acetic acid, or formic acid, are also sometimes used.,Acidizing,氢氟酸,盐酸,有机酸,醋酸,甲酸,Stimulation,Preflush fluids designed to prepare the formation for the ac

37、id, the acid plus its additives, and the displacing fluid that follows the acid, are all pumped at rates ranging from less than one barrel per minute to perhaps more than ten barrels per minute. The actual rates will depend on the calculated fracture pressure required to split the formations, and wh

38、ether a matrix or fracture treatment is preferred.,3,Acidizing,Stimulation,Volumes of 50 to 200 gallons of acid per vertical foot of formation are typical for most reservoirs, depending, of course, on the porosity and rock type. The acid solutions are delivered to the wellsite in specially lined tan

39、ks brought by truck to land locations and delivered by boat to offshore wells. High-pressure piping is connected to the well and the acid is pumped down the hole (fig. 2.7).,4,Figure 2.7 Acid is pumped from a truck down the well into the formation in a matrix-type acid job.,Acidizing,Stimulation,The

40、 idea was to pump fluid into a cased and perforated wellbore until the hydraulic pressure caused the formation to part; continued pumping would force the fluid into the fracture, propagating the fracture farther and farther from the wellbore.,5,Since that time, an enormous amount of research and fie

41、ld application of fracturing techniques have been carried out. Today, fracturing jobs that call for pumping over 1 million gallons of fluid and 3 million pounds of proppant are carried out (4000 m3 and 1.4 million kg). Such treatments, termed massive hydraulic fracturing (MHF), create fractures in t

42、he rock covering over 200,000 square feet (1300 m2), and extending thousands of feet from the wellbore. MHF costs may total 50% of total drilling and completion costs for some wells, hence it can be very important to optimize the fracture treatment design. It can be very important.,支撑剂,大型水力压裂,Fractu

43、ring,Stimulation,Although there is still some disagreement among theorists concerning the behavior of rock under stress, we now know that fracture orientation is dependent upon geologic conditions and that most fractures are vertical rather than horizontal (fig. 2.8).,6,Fracturing,Figure 2.8 Fractur

44、e orientation is dependent on geological stress conditions. Most fracture are vertical (a) rather than horizontal (b), although horizontal fracture do occur at shallow depths.,In order to significantly improve a wells productivity, a fracture must conduct fluid at a rate that is several orders of ma

45、gnitude greater than the conductivity of the rock itself. Creating a long, high-conductivity fracture involves selecting the appropriate fluid, additives, and proppant; determining the optimum volume of material to be pumped; pumping the material at the appropriate rate and pressure.,Fracturing,Stim

46、ulation,7,Desirable features for a fracturing fluid include the ability to remain in the fracture and not leak off into the formation, the viscosity necessary to transport the proppant out into the fracture, the ability to flow back into the well easily after depositing the proppant, and low cost. W

47、ater-based polymer solutions are popular, as are gelled hydrocarbons for water-sensitive formations. A wide variety of additives are available to reduce fluid friction in piping, prevent fluid loss from the fracture, control contamination, and ensure compatibility with the formation. The standard pr

48、oppant used to hold open the fracture is silica sand. Sand can be crushed, however, in deep formations where fracture-closure stresses are high. In such cases sintered bauxite, zirconium oxide, or other high-strength materials are substituted for sand. The goal is to create at least a partial monola

49、yer of proppant within the fracture, holding the fracture open, but not plugging it completely.,Fracturing,Stimulation,8,The volumes, rates, and pumping pressures are determined by the type of fracture desired. While it may be possible to pump a trainload of sand and a small lake of fluid into a wel

50、l high rates, it may not be economically practical. Simulation models, based on core data, can be used to generate data (fracture size as a function of fluid volume). When this kind of information is combined with the cost of a given treatment volume and the anticipated productivity increase related

51、 to fracture size, an optimum treatment size can be determined.,Fracturing,Stimulation,9,At the wellsite, the equipment required for a large fracturing job is somewhat more sophisticated than that required for an acid stimulation. Figure 2.7 shows the general layout. The fracturing fluid is held in

52、tanks, where any necessary additives are mixed. Proppant is sorted in similar containers, from which it is conveyed to high-rate blenders. Blenders combine the fracture fluid with the proppant and send the mixture to the pumping system.,Fracturing,Stimulation,10,混砂机,Figure 2.7 Equipment layout fo a

53、large fracture job.,Sand Control,1,A certain amount of sediment will always be produced along with formation fluids. Sand control is the technology and practice of preventing sand flow from unconsolidated sandstone formations. Such a problem is often found in Tertiary sediments at shallow depths, an

54、d in areas such as Nigeria, Indonesia, Trinidad, Venezuela, Canada, the U.S. Gulf Coast, and the Los Angeles Basin (Patton and Abbott 1982).,第三纪沉积层,Conception,Sand Control,2,Sand production leads to any or all of the following problems: casing collapse abrasion of downhole and surface equipment redu

55、ced productivity completely plugged (“sanded-up”) wells Methods for controlling sand production have generally involved one of two approaches: a metal screen and sand grain barrier that screens out the formation sand but does not inhibit fluid flow into the wellbore; or a epoxy resin that can be inj

56、ected into the formation near the wellbore and allowed to harden; this cements the sand grains together and by consolidating them prevents their movement (sand consolidation).,砂堵,环氧树脂,凝固，固化,倒塌，坍塌,Sand Control,3,In sand control, bridging methods employ wire-wrapped screens or slotted casing, both of

57、which have carefully sized openings that allow the formation sand to be deposited against them. In the case of gravel packs, carefully sized clean sand is placed outside the screen to retain the formation sand at its outer edge. Correct sizing of both the gravel pack sand and the gravel pack screen requires knowledge of the information about formation grain size distribution that had been obtained from cores. Guidelines have been developed to select sand and screen sizes that will pr