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1、The Haggis Field Exercise For Distance Learning Combined Question i.e. producing at rates lower than that is not feasible. Haggis-3 was drilled in May 1995. It is taken to be the case study for this field as it has average parameters for Haggis wells. Figure 1 is the completion diagram for Haggis-3.
2、 Above the wellhead, the well was completed with the same 5 1/2 OD production tubing encased in a mud line (no insulation). The mud line connects the wellhead (on the sea-bed) to the Xmas tree on the platform. For information, results of a recent pressure survey from Haggis-3 are listed in Table 2.
3、Depth 650 1605 2590 3600 4590 5587 6490 ft TVD Pressure 525 735 990 1292 1629 1920 2266 psia Table 2: Haggis-3 Pressure Survey The Haggis Field Haggis-3s well parameters, and results from both well testing and production logging are summarised in Table 3. Table 3 also contains data on Haggis-1. Hagg
4、is-3 and Haggis-1 are essentially twin wells, except that completion damage has resulted in Haggis-1 being considered the worst well in the field. Haggis-3 Haggis-1 Oil Production Rate 4730 3930 STB/d Water Cut 30 28 % WH Flowing Temperature 65 61 F Pressure at Xmas tree 445 psia Skin (Well Test) 2.
5、92 7.17 P.I. (J) (Well Test) 12.36 9.11 STB/d/psi Damaged Zone Relative Permeability 50 25 % Damage Zone Thickness 12 in Crushed Zone Skin 0.100 Drainage Radius 4000 ft Table 3: Well Data The Scenario: The rate of oil production decline in the Haggis field is alarming, and if no action is taken, Hag
6、gis will become uneconomical by the end of this year. The Operator of the field, Big Kahuna Oil Inc., does not accept this situation and has fired the fields former team leader for improper management of the field. Big Kahuna has hired you to improve production from the Haggis field. Your Mission: B
7、ig Kahuna Oil Inc. has asked you to study the fields potential. A model has been created using the company approved software (EPSs FloSystem). A variety of production proposals have been modelled and the outcome of these simulations has been provided in graphical form. It is your job to evaluate the
8、se proposals using the all the data provided. The report should outline: A) the model used in the study, B) the potential of the base case scenario, C) your assessment of production enhancement proposals from the Haggis engineers and D) your recommendation for a project which will enhance production
9、 from Haggis. Note: Wellflo graphs show gross production rates e.g. total production rates. Net production rates are required for the well analysis. The Haggis Field A) Develop a Well Model for Haggis-3: a) Using Haggis-3 as your case study, complete the missing data in Figure 2. b) The well Haggis-
10、3 is used as the base case well for the Haggis field throughout this exercise. To minimise the computer time involved in simulations, the model contains only those components that contribute significantly to the pressure drop along Haggis-3. These are shown on Table 4. Node No. Component Name Measur
11、ed Depth (ft) 1 Outlet node / Wellhead 0 2 Riser 350 3 Xmas tree 350 4 5.5” Tubing 850 5 S.C.S.S.S.V 850 6 5.5” Tubing 4000 7 5” Tubing 5600 8 7” Liner 6530.5 Table 3: Well Data Compare this model to the completion design in Figure 1. When would it be necessary to include the nipples and tubing cons
12、trictions in the model design? _ _ 2.5% c) The Outflow curve for Haggis-3 was modelled using a number of well-known correlations. The sensitivity analysis is shown in Figure 3. The correlation that is most appropriate is: _ 2% There are two main reasons why this correlation was chosen: 1) _ _ 2) _ _
13、 _ _ _ _ 2.5% d) The Big Kahuna Oil Inc. is unfamiliar with the concept of nodal analysis used in this flow simulation. You are asked to explain the process and the conditions for flow stability. The inflow-outflow diagram below is for Haggis-3 at 30% water cut and utilising an appropriate flow corr
14、elation. The Haggis Field Curve A Curve B Point D Point B Point C Point A Point E Diagram 1: Haggis-3 base case ? Curve A represents the _. ? Curve B represents the _. ? The reservoir pressure is _psia (Point_). ? The_ IPR model was used to produce this curve. Why was this chosen? _ _. ? Point _ rep
15、resents the operating point. The operating point is stable/unstable. Explain: _ _ _. Nodal analysis may be carried out at any point in the producing system. In this report, the analysis was carried out to find the operating point at the sandface (see above diagram). Other typical examples of nodes s
16、elected during completion design are: 1)_to evaluate _ 2)_to evaluate _ 11.5% The Haggis Field B) Base Case Analysis: As a good manager, the first thing you have to do is evaluate the potential of what you have at the moment. To achieve that, you must determine what effect the decline in reservoir p
17、ressure and the increase in water cut will have on Haggis-3s production if nothing is done to improve its production. In other words, determine the reservoir pressure and the water cut at which Haggis-3 will becomes uneconomical to produce under the current production scenario. a) In order to evalua
18、te the viability of producing Haggis-3 as water-cut increases and reservoir pressures reduces, a number of sensitivity analyses were performed on the production from Haggis-3 using WellFlo. These sensitivities are illustrated by Figures 4a, b, c and d, and their results should be summarised in Table
19、 5: PRes. WC 2800 2700 2600 2500 psia 30% 4770 35% 40% 45% Table 5: Haggis-3 Production Forecast 4% b) You discuss these figures with the fields engineers. Since artificial lift can not be supported by the production facilities on the Haggis platform, you agree with your engineers that you have to s
20、tart a water injection scheme to maintain the reservoir pressure at 2800 psia. Figure 5 shows the well sensitivity to water cut. Under these circumstances, Haggis-3 will produce economically (1500+ BOPD) at maximum water cut of _, and at an oil production rate of _ BOPD. This is considered to be the
21、 Base Case scenario, against which all other schemes in section C will be compared. Scenario Maximum Economic Water Cut Production Rate 30% Water Cut Base Case c) With a water injection scheme in place, you expect to face even more severe water production from Haggis-3. One way of dealing with such
22、a problem is to plug-off “watered-out” perforations. List two advantages and two disadvantages of this scheme. Advantages: 1)_ _. 2)_ _. Disadvantages: 1)_ _. 2)_ _. 5% The Haggis Field d) A sensitivity study is outlined in Figures 6a, b and c for three plugging-off policies. Based on the advantages
23、 and disadvantages you identified above, the most advantageous plugging off policy is:_. The minimum open interval at which Haggis-3 will produce economically under this policy is _ft. 2.5% C) Further Projects: You phone management and convince them to fund the pressure maintenance scheme. In additi
24、on, they agree to provide a budget for an extra project to improve Haggiss production. In this section you must select the best project from your engineers suggestions below. Since production, and thus revenue, from Haggis is greatly affected by water production form the field, Big Kahuna Oil Inc. d
25、efines the best production enhancement project for the Haggis field as the one that sustains economical production form Haggis-3 at the highest water-cut. Therefore, this should be the criterion you use to select the project you recommend to management. C.1) Production Technology Solutions: You walk
26、 into the teams senior production technologist office, and give him the good news from management. He congratulates you, and immediately suggests that the project should be a production technology project. He goes on to explain that as the Haggis wells are extremely damaged, acidising all the wells
27、make the field very profitable. a) Determine the benefit from acidising Haggis-3 in terms of the maximum water cut at which the acidised Haggis-3 will sustain economic production, if acidising restores the original rock permeability. Figure 7 shows the sensitivity of Haggis-3 to water cut after acid
28、ising. The maximum water cut at which the well can produce economically is _%. Scenario Maximum Economic Water Cut Production Rate 30% Water Cut Acidising (Use this result to compare the benefits from this project to the other proposed projects, and as a basis for your recommendations in section D).
29、 b) A production model of well Haggis-1 is already available and shows that Haggis-1 will produce economically at maximum water cuts of 50 % after acidising. What are the implications of this if it is decided to carry out a campaign in which all the Haggis wells are to be acidised? _ _ _ 3.5% The Ha
30、ggis Field c) The diagram below shows the inflow-outflow curves for Haggis-3 at the maximum economic water cut after acidising. Assuming that acidising succeeds in restoring the original rock permeability in both wells, sketch on the diagram the inflow-outflow curves for Haggis-1. Diagram 2: Haggis-
31、3 after acidising 2% C.2) Suggestions from the Drilling Engineer: The drilling engineer walks into your office and says that he heard that you were going around the different departments asking for ideas on how to improve the fields production. He says that he could have saved you all the trouble be
32、cause he has the perfect solution. Side-track the well, he says. He goes on to explain that, he would have gone for a horizontal well. However, since Big Kahuna have recently had bad luck with drilling horizontal sections longer than 400 ft, a 75 deviated well through the reservoir is probably the b
33、etter option from a drilling point of view. a) Given the drilling departments recent experience with horizontal wells, should you side-track Haggis-3 to a 400 ft horizontal well running through the middle of the reservoir or propose a 75 deviated well penetrating the whole of the reservoir height? T
34、he production prognosis from Haggis-3 sidetrack as a 400ft horizontal well is shown in Figure 8 while a 75 deviated well is illustrated in Figure 9. Summarise the results in the table below: Option Scenario Maximum Economic Water Cut Production Rate 30% Water Cut C2.a1 400ft Horizontal C2.a2 75 Devi
35、ated Option C2.a2 produces the better results because: _ _ 3% The Haggis Field b) Given the engineering and economic factors and assumptions below, design the optimum horizontal well (to the nearest 500-ft) for the Haggis-3 side-track: Length of build-up section is: 2000 ft-MD Pay-back Time: 6 month
36、s Side-track cost: US$850 /ft-MD Price of Oil: US$15/bbl Cost of Processing and Shipping: US$8 / bbl Assumptions: 1) Economics based on un-dicounted cash flows 2) Production rate is constant for the first 6 months 3) Use Profit to Investment Ratio as measure of value, see below. (Profit to Investmen
37、t (PI) Ratio = TCS/MCO where TCS is Terminal Cash Surplus and MCO is Maximum Capital Outlay. The PI ratio is a measure of the cash surplus or profit generated for every unit of currency invested.) Table 6 below can be completed using the results from Figure 10 and taking in account the above enginee
38、ring and economic factors for drilling horizontal wells. Horizontal length (ft)5001000150020002500300035004000 Parameter and unitFormula Table 6:Economic analysis of sidetracking Haggis-3. (In the space above, enter the parameter, formulas used and intermediate working) Table 6 indicates that the optimum horizontal section length for Haggis-3 is _ ft. However, by carefully analysing the economic outcome and technical aspects of the design, what other conclusion could be drawn? _ _