Copyright 2001, Society of Petroleum Engineers Inc. This paper was prepared for presentation at the SPE Latin American and Caribbean Petroleum Engineering Conference held in Buenos Aires, Argentina, 25–28 March 2001. This paper was selected for presentation by an SPE Program Committee following review of information contained in an abstract submitted by the author(s). Contents of the paper, as presented, have not been reviewed by the Society of Petroleum Engineers and are subject to correction by the author(s). The material, as presented, does not necessarily reflect any position of the Society of Petroleum Engineers, its officers, or members. Papers presented at SPE meetings are subject to publication review by Editorial Committees of the Society of Petroleum Engineers. Electronic reproduction, distribution, or storage of any part of this paper for commercial purposes without the written consent of the Society of Petroleum Engineers is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of where and by whom the paper was presented. Write Librarian, SPE, P.O. Box 833836, Richardson, TX 75083-3836, U.S.A., fax 01-972-952-9435.

Abstract Slim hole wells are usually associated to lifting efficiency problems, specially when completed with very reduced diameter, which is usual in marginal fields to decrease costs and improve profitability.

The objective of this work is to give insight into results obtained using a non-conventional sucker rod pumping in pumping wells of 2.7/8” in diameter. The principal characteristic of the system is the replacement of sucker rods by 1” maccarroni tubing, which reciprocate the pump plunger and direct the flow to the surface. The most important task was to calculate the appropiate pumping action as to have minimal risk to the well. The same is considered in the modification of the equipment of subsurface (sucker rod pump and maccarroni), polished rod and stuffing box. Introduction The challenge of producing the wells cased with very reduced diameter (2.7/8”) efficiently resulted in using 1” maccarroni in substitution of the sucker rods to transmite the surface pumping motion and power to the subsurface pump, which at the same time works as tubing in shallow well of low production.

Maccarroni has been used in the industry for many years, mainly to produce from the wells of low production with different types of gas intermittent lift systems, such as : Crossover, Snorkel and Parallel.

The most important task was design the appropriate way of pumping that assures the least fishing risk for the well, the same one that considers basically the modification of the

subsurface equipment (the subsurface pump and 1” tubing), polished rod and stuffing box.

This innovative design outlined in 1998, before the necessity of producing five (5) slim hole wells efficiently. The wells were completed in 1996 and put in production with conventional gas lift (without packer) with a pressure of 280 psig. However, the reservoir flowing pressure continuously decline from 300 to 200 psig, then the pressure of the injected gas counteractued the drainage of fluids of the reservoir, to such a point that the wells were loaded and stopped producing.

This design allows to produce wells of reduced diameter at smaller cost compared with the wells of higher diameters equipped with sucker rods and 2 3/8” tubing. Discussion Equipment selection As shown in figure 1, following innovations are seen: Subsurface equipment. The type of subsurface sucker rod pumps prefered is RWTP as indicated in Table 1, although types RWBP, RWAP; RHAP y RHBP with the appropriate connections could be used, including important innovations:

- Pumps sealant is replaced by a compression anchor, which is responsible for hold down the pump at the desired depth.

- Guide rods on the top of the barrel are replaced by a connector between the working barrel and maccarroni tubing.

- Sucker rods are replaced by 1” or 1 ¼” maccarroni. Surface equipment. Following innovations have been introduced comparing with standard installations :

- Instead of the conventional polished rod, the same maccarroni tube is used with a polished rod liner to protect it.

- The use of a high pressure hose to connect the upper end of the maccarroni to the flow line. Calculations In accordance with the configuration for the subsurface equipment in Figure 1 and the following technical data , the design is made according to the calcultation procedure from acceleration factor , as shown:

SPE 69550

Non Conventional Sucker Rod Pumping for Slim Hole Wells Mario Alva and Anthony Alfaro, Perez Companc

2 M.M. ALVA, A. ALFARO SPE 69550

Data : - J 55 Maccarroni tube: Nominal diameter = 1 ¼ in.. Internal diameter = 1.38 in. External diameter = 1.66 in. Cross sectional area of maccarroni = 0.66853 in2. External diameter of the coupling = 2.20 in. Weigth per feet = 2.40 lbs/ft Capacity of maccarroni = 1.85 bls/1000 ft Joint Yield Strength (maccarroni ‘NU’) : 31950 lbs - Depth of the well = 1500 feet - Depth of the subsurface pump = 1200 feet - Expected production = 45 bls/día Calculations. For pumping unit API 80-133-54, working with 54 and 8 spm and rod pump of 1 ¼", with procedure of the Appendix we have: - Expected production :. PD = 0.146 * 8 * 54 = 63 bpd - Loads and Torque : FT = 26.45 c = 24" h = 74.5" A max-a = 0.06481 * g A max-d = 0.03323 * g WMACCARRONI = 2.4*1200 = 2880 lbs WFLUID = (1.05*8.33)*(1.85*1200*42/1000) = 815.5 lb Then: PPRL = (2880 + 815) * (1 + 0.06481) = 3935 lbs MPRL = 2880 * (1 - 0.03323) = 2784 lbs CBE = (3935 + 2784) / 2 = 3359 lbs TORQUE = (3935 - 3359) * 26.45 = 15208 in.-lbs - Maximum stress (SA) : Smin = 2784/0.66853 = 4164 psi Smax = 3935/0.66853 = 5886 psi SA = (0.25*31950 + 0.5625*4164) = 10330 psi Comparing the last two results it is seen that Smax < SA , therefore the stress are inside the allowable range of stress. If the obtained values exceeded the values allowed by the pumping unit (Torque = 80,000 inch-lb; PPRL = 13300 lbs) and the required production was different to the desired, another calculation is made changing the condictions of operation of the pumping unit, for example if we change to a smaller stroke (with 45 inch in this case), the new values of the variables would be: - Expected production : PD = 0.146*45*8 = 53 bls/día - Loads and Torque : FT = 22.218

c = 20" h = 74.5" A max-a = 0.05182 * g A max-d = 0.02988 * g WMACCARRONI = 2.4*1200 = 2880 lbs WFLUID = (1.05*8.33)*(1.85*1200*42/1000) = 815.5 lb Then: PPRL = (2880 + 815) * (1 + 0.05182) = 3886 lbs MPRL = 2880 * (1 - 0.02988) = 2794 lbs CBE = (3886 + 2794)/2 = 3340 lbs TORQUE = (3886 - 3340) * 22.218 = 12131 in.-lbs - Maximum stress (SA) : Smin = 2794/0.66853 = 4179 psi Smax = 3886/0.66853 = 5812 psi SA = (0.25*31950 + 0.5625*4179) = 10338 psi Following the Modified Goodman procedure, maximum depth to which this system can be used, (because of J-55 maccarroni Yield Strenght), is shown in tables A and B (2500 ' for 1.1/4 and 1900 ' for 1"): Table A: 1” maccarroni. Depth (ft) 1200 1500 1900

PPRL (pd) 2802 4919 6558

MPRL (pd) 2088 3480 4408

CBE (pd) 2445 4200 5319

TORQUE (pd-in) 9443 19023 24096

SA (psi) 10002 11587 12644

SMAX (psi) 5674 9960 12615

Table B: 1 ¼ ”maccarroni

Depth (ft) 1200 1500 2000 2500

PPRL (pd) 3935 4919 6558 8526

MPRL (pd) 2784 3480 4640 6033

CBE (pd) 3360 4200 5599 7279

TORQUE (pd-in) 15219 19023 25364 25364

SA (psi) 10330 10916 11892 13063

SMAX (psi) 5886 7358 9810 12753

SPE 69550 NON CONVENTIONAL SUCKER ROD PUMPING FOR SLIM HOLE WELLS 3

Installation sequence This system implies a new methodology for the installation and production of wells, such as when running the RWBP pump: · Connects the dip tube to the compression anchor, that also acts as the pump sealant, that is of the type modified hollow. The barrel carries on its upper part a modified “hollow valve” pull tube. · Places this unit into the well supporting it with a maneuver grip. · Connect the hollow valve pull tube with the maccarroni with an adequate crossover (API part C13-175) · Pull down the subsurface pump and the maccarroni carefully. · When it reaches the desired depth, hold the maccarroni with a friction grip and cut the maccarroni off as necessary and prepare the thread. · Place the maccarroni piece with the liner rod, locating this last one in the run area. Adjust appropriately. · Space the pumps and load the compression anchor, place the polished rod clamp, dynamometer device and finally support all the pumping string by the carrier bar of the pumping unit. · Place a flexible hose in the upper end of the maccarroni, by means of elbows and crossover (Figure 1). · Connects the other end from the hose to the production manifold. · Put the well in operation. Advantages and disadvantages Advantages: · The main advantage is produce the well at maximum capacity, combining the capabilities of beam pumping assuring as much draw down as possible to obtain maximum production rates. · Uses the same surface equipment (pumping unit and prime mover ) as those of the rod pumping. Disadvantages: · Less annulus space causes a quicker paraffines accumulation. · Precision is required to load the anchor and misoperation could discharge it. · Friction of maccarroni couplings could cause premature wear and breaks of both maccarroni and casing, and fishing problems. Results This lift system: ! Has successfully solved the problem of production in shallow, low diameter wells allowing a much lower cost for well construction (10 vs. 7 when comparing 9 5/8 – 5 ½ with slim hole 5 ½ - 2 7/8 wells). ! Improve operational efficiency when compared with previous slim hole artificial lift from 8 to 38 bpd (250 %). ! Allowed to recover 24,500 bbls in the first year and expected 128,400 bls until reaching economic limit.

! Significantly reduced pulling jobs, thus reducing operational costs. ! Have been in operation for more than 26 months without interruptions. Conclusions

1. An altenative to rod pumping has been tested to produce 27/8” slim hole wells, which basically modify the subsurface equipment, polished rod and stuffing box.

2. Tubing and sucker rods are replaced for 1” maccarroni being the system suitable to reactivate marginal fields with slim hole wells at low costs.

3. A new working methodology has been developed for optimum operation.

4. RWTP type sucker rod pumps are recommended. If free gas is expected, other pumps with traveling plunger and appropriate gas separator can be used. Nomenclature

A max-a = upward maximum acceleration, ft/sec A max-d = downward maximum acceleration, ft/sec

Ap = cross sectional area of the plunger, in2 At m = cross sectional area of the maccarroni, in2

c = Length of the crank, in CBE = effect of counterbalance, lb

FS = service factor g = gravity acceleration = 32.2. ft/sec2

Gw = specific gravity of produced water h = length of the arm (pitman), in K = constant L = pump depth, ft

Lm = length maccarroni, ft MPRL = minimum polished rod load, lb

N = speed of pumping, spm wm = weigth of maccarroni for foot lb / ft

WMACCARRONI = total weigh of the maccarroni string, lbs WFLUID = weight of produced fluid

PD = expected production , bpd PPRL = peak polished rod load, lb

FT = torque factor. SA = maximum allowable stress, psi.

Smax = maximum stress, psi Smin = minimum stress, psi

Sp = effective stroke of the plunger, in T = minimun tensile strength, psi

Torque = gear reducer torque, in -lb Vm = capacity of maccarroni (bl/1000 line feet)

ASA = Maximum allowable range of stress, psi

Acknowledgments To Perez Companc for allowing the publication of this paper. Apreciation for their concurrence and support in implementing the installation at five wells of Laguna field is extended to S.

4 M.M. ALVA, A. ALFARO SPE 69550

Maguiña Production Engineer and J. Arone Production Engineer. References 1. Kermit Brown: “The Technology of Artificial Lifts

Methods”. 2. Nind, T. E. W. : “Principles of Oil Well Production” 3. “API Recommend Practice for Care and Handling of

Sucker Rods”. Appendix – System Design In accordance with Figure 1, the design is made from the acceleration factor procedure , as shown: Data - Maccarroni tube: Nominal diameter: 1 ¼ inch Internal diameter: 1.38 inch External diameter: 1.66 inch Traverse area - maccarroni: 0.66853 inch2 External diameter of the couple: 2.20 inch Weigth per feet : 2.40 lbs/ft Capacity: 1.85 bls/1000 ft Degree: J - 55 Joint Yield Strength (maccarroni ‘NU’) : 21360 lbs - Depth of the well: 1500 feet - Depth of the anchor: 1200 feet - Expected production: 45 bls/día Calculation procedure : - Expected Production: PD = 0.1484 Ap*Sp*N . . . . . . . . . . . . . . . . . . . . . . . (A-1) Where: 0.1484 = Constant conversion factor Normally the previous equation is used with a constant “K” which involves Ap, 80% of “S” and the conversion factor. Then, the equation changes to: PD = K*S*N . . . . . . . . . . . . . . . . . . . . . . . . . . (A-2)

- Maximum load in the upper part of the string of maccarroni tube (PPRL) is:

PPRL = WMACCARRONI + WFLUID + (WMACCARRONI + WFLUID) * A max-a / g . . . . . . . . . . . . . . . . . . . (A-3) Where : WMACCARRONI = wm * Lm . . . . . . . . . . . . . . . . . . . . (A-4) WFLUID = Gw*8.33 lb/gal *Vm*Lm*42 gal/bl . . (A-5)

A max-a = (S*.N2 / 70500)* (1+ c/h) * g . . . . (A-6) · Minimum Load (MPRL) in the upper part of the string of

maccarroni tube is: MPRL = WMACCARRONI + (WMACCARRONI) * A max-d /g (A-7) Where : A max-d = (S*.N2 / 70500)* (1 - c/h) * g . . . . . (A-8) · Effect of Counterbalance, is : CBE = (PPRL + MPRL ) / 2 . . . . . . . . . .. . . . . . (A-9) Maximum Torque on the Gear reducer : Torque = (PPRL - CBE) * F.T.90° . . . . . . . . . (A-10) Maximun Stress:

Maccarroni tubing is subjected to a continuous work of variable and recurrent loads. To define if the range of stress is below the maximum avalaible stress from Goodman’s modified diagram,

SA = ( 0.25*T + 0.5625*Smin)*FS . . . . . . . . (A-11)

TABLE 1 - HOLLOW MODIFIED PUMP 25 - 125 - RWBP

Description N° API Assembly of the plunger

1 Reduction to maccarroni 2 Cage, closed plunger C13-175 3 Ball and seat V11-175 4 Hollow pull tube valve connector 5 Pull tube T11-125 6 Coupling upper pull tube C32-125 7 plunger P21-125 8 Ball and seat V11-125 9 Cage, closed plunger P12-125

10 Plug, seat Assembly of the working barrel

11 Guide of modified hollow pull tube valve 12 Upper connector of modified barrel C21-20-125 13 Barrel B12-125 14 Cage, closed barrel C14-20-125 15 Ball and seat V11-175 16 Bushing, seat B22-20

Assembly of the anchorage packer 17 Reduction of the B22-20 to the packer 18 Packer of anchorage without rubbers

SPE 69550 NON CONVENTIONAL SUCKER ROD PUMPING FOR SLIM HOLE WELLS 5

Fig. 1 - Nonconventional Sucker Rod Pumping

SURFACE :

CELBOW 2"

XOver 2" - 1 1/4"

WIRE

LINER HOSE

MACCARRONI

UNION

FLOW LINE

STUFFING BOX

CHECK VALVE

CASING GAS

SUBSURFACE

RESERVOIR

MACARONI OF 1 1/4"

CONNECTOR TRAVELING VALVE

MACARRONI-BARRIL

BARREL

CHAMBER

STANDING VALVE PUMPTYPE RWTP

PLUNGER

ANCHOR

RESERVOIR

DIP TUBE

CASING 2 7/8"