SPE-173601-MS - Petroleum Engineer's Club of Dallas · located between the Llanito and Galan...

SPE-173601-MS Reduced Emissions and Increased Production

Through Gas Compressors: Pilot Case in Colombia

J.C.M. Escobar-Remolina, SPE, Ecopetrol S.A.; W. Barrios-Ortiz, L. Franco-Sandoval, J. A. Sachica-Avila, Ecopetrol S.A.;

C. McCoy, Permian Production Inc.; R. D. Rios-Recuero, Imgeprom Ltda.

Session 10, Remediation – Shale Formations from 3:30 pm – 4:00 pm

Abstract

REDUCE GREENHOUSE GAS INCREASE OIL PRODUCTION INCREASE DHP EFFECIENCY

In this work we show how using walking beam gas compressor technology, typically installed on a centrally located pumping unit, on six unprofitable wells, reduces greenhouse gas emissions to the atmosphere and increases oil production in the selected pilot area for this technology application.

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After installing beam gas compressors on each well, its oil production rose on average by 35%.

Green House Gases were no longer allowed to emit into the atmosphere.

33 000 tons of CO2 equivalent had been emitted. The Colombian state oil company is very satisfied because they

have succeeded to:1. Relieve restricting backpressure2. Capture and compress vented gas To avoid gas flaring3. Convert marginal wells into profitable ones.4. Cut labor cost by relieving personal from the operation of

venting or flaring. Made the six wells profitable again and leverage field production

with very few maintenance problems. We have other projects in the making in these and other

formations to achieve the same results. Keywords: CO2 equivalent; beam gas compressors technology; Greenhouse gas emissions; Increased Production; Mechanical pumping.

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Introduction

As the wells produce and the natural drive of the reservoir diminishes over time.

The natural downhole pressure reduces over time. Artificial Lift systems are introduced. 90% of artificial lift worldwide is the mechanical pumping

(Nazi and Lea, 1994; Tripp, 1989). Formation backpressure becomes a problem and

restricts production. I the case of Colombia most wells producing oil have to

vent the casings to the atmosphere to produce the oil and this gas has to be burned.

Flaring presents environmental problems and high operating risks and cost (Gallo et al., 2002; Sandler et al., 2012).

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The walking beam gas compressor technology is widely used in the petroleum industry worldwide due to its low operating cost and system functionality.

In 1979 Charlie McCoy, inventor of the BC, made his first installation in a well of an oil company in West Texas.

The Colombian state oil company decided to run a pilot test in 6 wells at Colombian fields to determine the behavior of this technology.

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PILOT PROJECT LOCATION

The pilot test area was established in two zones called Lizama Zone and North Zone, both belonging to the basin of the Medium Magdalena Valley, determined by the following location, as shown in Figure 1. Figure 1 shows the exact location of the zones where this pilot project is held in the basin of the Medium Magdalena Valley. Lizama Zone: Includes Lucama, Nutria and Tesoro fields, located at the eastern end of the area of the Superintendence in the town of San Vicente de Chucurí. North Zone: Includes Llanito field (located at the north of the town of Barrancabermeja), and Gala field, which located between the Llanito and Galan fields, all in the municipality of Barrancabermeja

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SELECTED WELLS DETERMINING FACTORS

The wells suitable for pilot test of the beam compressors were named: GAL1, LLA1, LIS1, NUT1, NUT2 y TES1. These wells are candidates to receive the beam compressor technology, since their fluid moves from the reservoir to the surface and its trip through the transportation pipelines and treatment plants have the following detriments:

� The backpressure to the face of the formation is very large.� The well production decreases. � Interference in the downhole pump due to gas.� Operating costs because of early failure in the rod or in the production line. � The gas is sent to the Atmosphere. � The gas is burned, expelling pollutant gases into the atmosphere.

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Overview and Theory of the walking beam compressors system

FORMATION PRESSURE DECLINES SERVICE PRESSURE CAUSES FORMATION BACK PRESSURE THE WBGC REDUCES CASING PRESSURE AND FORMATION BACK PRESSURE FORMATION IS ALLOWED TO PRODUCE AT ITS MAXIMUM RATE WITH INCREASED FLOW

INTO THE WELLBORE. THE WBGC USES ENERGY FROM THE EXISTING PUMPING UNIT.

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How the Walking Beam Gas Compressor Works

THE WALKING BEAM GAS COMPRESSOR IS A DOUBLE ACTING COMPRESSION SYSTEM.

FOUR CHECK VALVES CONTROL THE COMPRESSION CYCLES AS THE PISTON TRAVELS THROUGH THE STROKE

GAS AND PRESSURE ARE DRAWN FROM THE CASING AND THE GAS IS THEN DISCHARGED INTO THE FLOW LINE CLOSE TO THE PUMPING TEE.

The Figure 2 describes the basic principle of how the compressor works when extracting and discharging the gas from the well to the production line.

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Figure 2. Lower Suction (left) and upper (right) of the WBGC Technology.

Design Criteria of the Walking Beam Gas Compressor

PRESENT GAS VOLUME (MCFD) FLOW LINE (PRDUCTION LINE) PRESSURE INFORMATION REGARDING THE PUMPING UNIT (MODEL, MAKE, ETC.) STROKES PER MINUTE PERCENTAGE OF RUN TIME CAPACITY OF WALKING BEAM GAS COMPRESSOR (SIZE OF PISTON AND LENGTH OF

STROKE) SUCTION PRESSURE (DESIRED CASING PRESSURE) TO WBGC (PSIG + APSI)

The WBGC comes in diameter sizes from 5 inches to 18 inches. The length of the WBGC will be determined by the stroke available on the existing Pumping Unit.

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From above the second concept arises. Productivity Index (J). EI productivity index reports the production capacity of a well and is used to characterize in relative way the different formations. It is common to find those whose productivity rates are less than one and formations with a much higher capacity productivity rates that goes to several tens. The analysis of a production system, based on the flowing bottomhole pressure (Pwf), requires to separate our system into two, one going from the reservoir (Pr) to downhole (Pwf), and another that goes from the well down the production tubing, reaching the wellhead and ends in the separator. Then, depending on the dynamic pressure (Pwf), the flow rate and the analysis of the force necessary to overcome the pressure drops across the route from the reservoir to the separator, it will be considered whether an external lift system will be necessary. This system will provide enough energy to the fluid in such a way that it will overcome these constraints, and also responds the question of how to provide the energy for these systems. A typical curve for the above can be seen in Figure 3 and Equation 2 provides the mathematical definition of J.

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This equation J, where viscosity is not shown, it was replaced by Escobar-Remolina et al., 2012 for the functional form .

In Equation 2, the symbol % means composition, as seen J equation so expressed represents all planes of PVTx. In this work, the functionality Escobar-Remolina et al., was adapted for the first time to the concept of productivity index. This enables us greater flexibility as to the parameters that include variations in the systems by temperature and composition, it further pairs the concept of J (Equation 2) to the design concept (Equation 1). This represents a real advantage for the comprehensive management of the fluid, the formation, and production systems from the reservoir to the delivery points, i.e. flow assurance. Equation 2 expressed in this way, was essential to simulate the problems of paraffin that arose in some of the wells in the pilot test performed at Lizama. Equation 2 correlates the compositional changes by precipitation of paraffin obtained by thermodynamic modeling (Pedersen, 1993; Escobar-Remolina, 2006) with the J index and rheological changes.

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Application of Beam Compressor Technology and Results For this section the well LLA1 was taken as reference for the Northern Zone and Zone Lizama, NUT2 was chosen. The other four (4) wells show similar results and will not be presented in this article

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Table 1 clearly indicates an increase in production of 36%.

A reduction of 7241 tons in CO2 equivalent emissions.

The efficiency of the DHP at the well LLA1 improved 40%.

Before the installation these emissions were burned or released into the atmosphere. Furthermore

Figure 5 shows the beam compressor installed at Well NUT2, front mount type, combining the techniques of design and PVTx analysis the optimal design was achieved for this well, so that its impact on production and CO2

equivalent emissions and other variables have a positive character for the operation of the oil field in the Lizama area.

Figure 5. BC Technology installed in the Area Lizama for well NUT2

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Figures 6 shows the increase of production after installing the technology.

The gain in production for Well NUT2 is 39%.

and the behavior of annular pressure over time, respectively.

For the months after the installation it can be seen how the production increases, reaching about 50 barrels/day on average

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This BG generated noise at NUT2 and was due to particular behavior of the formation (crystallization of paraffin) but not BGC malfunction.

This precipitation of paraffin was analyzed and installing a lubricating system was recommended.

The BC was adapted to the specific characteristics of the well, showing the versatility of the BGC for different extreme conditions.

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Figure 7 shows how the annular pressure decreases with time, generating it a clear improvement in the J of wells since flowing bottomhole pressure (Pwf) is smaller, so it can be expected an increase in oil production.

The CO2 equivalent emissions of the well NUT2 that were released into the atmosphere are shown in Table 2 together with emission reductions in tons of the other 5 wells in the North Zone and Lizama.

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Table 2 shows that it was possible to stop venting 32 820 tons of CO2 equivalent using beam compressor technology. This is important because every undertaken project must conserve and sustain environmental systems, so we are going to be able to say what project might harm the environment and should not be run.

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Conclusions A working philosophy was defined and applied We integrated the concepts of design, the productivity index and PVTx analysis, introducing the

productivity index equation that incorporates these concepts. After installation of beam compressors oil production wells each rose on average by 35%. Beam Gas Compressors made six wells to be profitable again and leverage the field production with

very few problems and maintenance. During the pilot test it was observed that none of the 6 wells released or burned gas. In our pilot test, over 33 000 tons of CO2 were not released to the environment over a period of nine

months. It was determined that the WBGC technology gave us a significant reduction of equivalent CO2

emitted in the production of our oil. The drawbacks we had experienced in the production of the six wells of the pilot test disappeared as

a result of the installation of the walking beam gas compressor technology:1. The back pressure to the face of the formation2. Interference of gas in the Down Hole Pump3. Reduction in operating cost due to reduction in early failures in the rod string and the production

tubing.

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Acknowledgements J.C.M Escobar-Remolina and W. Barrios want to thank the following:Flow Assurance Group (GAF) from the EOR Department of GDY at Ecopetrol S.A,engineer Francy Edith Ramirez (GMM), geologist Adriano Lobo and engineer Carlos Chaparro for his collaboration in this test technology.

J.A. Sáchica and L. Franco thank all the staff of engineering at SOM - Ecopetrol S.A. R. Rios-Recuero and Charlie McCoy thank the Ingeprom SAS task force, especially the Project Manager Jorge Darío Suárez. All authors give special thanks to the production group of SOM-Ecopetrol S.A, for their collaboration in particular the Engineer Ivan Alfonso Romero.

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Questions

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What type of well qualifies for the walking beam gas compressor technology?

How much energy does it take to operate the equipment? Can this equipment be moved from well to well? What is the average life of this system of compression? What if we need to change the stroke length on the PU? What line pressure can this technology compress into? Can we pull a vacuum if we need to? What about H2s, CO2 and other corrosive properties we

find in the Oil Patch?

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