Gas Lift Optimization To Improve Production Of Oil In a Reservoir

ABSTRACT

Hydrocarbon especially oil & gas are mostly used worldwide as an energy source, during the production of hydrocarbon under natural depletion, reservoir energy is recognized as the cause of fluid flowing into the well and producing in the surface. By producing from the reservoir and increasing pressure, natural production declines and eventually stops, artificial lift methods are needed when buttonhole pressure is not enough to bring up the oil to the surface.

This study presents optimization of the production conditions of a well by using artificial lift methods such as the gas lift system. A single well model is created to predict future production conditions in the good drainage area and the recommended optimum production conditions. The next step is to try to evaluate the parameters affecting the selection of an artificial lift method. Also, looking at the advantages and disadvantages of the various artificial lift methods in regards to oil production.

Finally, considering the technical and economic aspects of each method, different approaches are compared to determine the optimum production scenario via artificial lift designs. The results of this study show that both gas lifts can achieve the desired well flow rate in the studied field. However, in terms of cost and the net present value of the project, gas lift is more economical.

Well, level optimization is often achieved by optimizing the good parameters like the point of injection, injection rate, and injection pressure.

All these aspects have been investigated and presented in this study by using experimental

data and the PROSPER simulation program. The results show that the wellhead pressure has

a large influence on the gas lift performance and also proved that smart gas lift valves can

be used to improve gas raise performance by controlling gas injection from the downhole.

Obtaining the optimum gas injection rate is very important as a result excessive gas

injection reduces production rate and consequently will increase the operational expenditure.

CHAPTER ONE

INTRODUCTION

A gas lift is an artificial lift that uses pressurized gas into the wellbore to improve production. The principle of gas lift is that gas injected into the tubing reduces the density of the fluids in the tubing, and the bubbles have a scrubbing action on the liquids.

This method is not by any means new to the oil & gas industry. For the oil& gas trade, the gas lift was utilized in Pennsylvania to assist production in oil wells in 1864. The compressed air was used as an air pipe that brought the air to the bottom of the well. Since then, we’ve tailored and formed this methodology into the strategy we tend to use these days.

Historically, both natural gas and air have been used in gas injection projects, and in some cases, nitrogen and flue gases have been injected Many of the early gas injection projects used air to immiscible displace crude oil from reservoirs.

The injection of hydrocarbon gas might lead to either a mixable or immiscible method counting on the composition of the injected gas and petroleum displaced, reservoir pressure, and reservoir temperature.

1.1 BACKGROUND STUDY

Gas lift is a type of artificial method that is currently being used in most the oil
the field across the world and the reason behind that is its wide range of applications and particular characteristics which includes flexibility in the production rates of oil and depth which makes it superior over other artificial lift methods, gas lift method is applicable and suitable for the highly deviated wells in which dogleg severity is extremely high and it can handle sand production, unlike ESP because of the absence of any moving mechanical equipment.

The effective design of the gas lift system is very important so that the gas lift system should adhere and cope with the changing conditions of the reservoir.

Pressure depletion can cause reservoir compaction and water injection is used as a remedial action for maintaining the reservoir pressure but with time problems occurs such as increased water cuts which will increase the hydrostatic head pressure in the tubing resulting in decreased production rates and efficient gas lift operation.

To address these problems, the compression unit of the gas lift system should be capable of delivering an increased volumetric capacity of gas at sufficient discharge pressures.

A multi-stage compression unit can deliver the discharge pressures that are sufficient for well kick off if required as well as for normal continuous gas lit operations.

The use of electrical motors as prime movers provides a great amount of flexibility to the compressors in terms of the operating parameters that are flow rate and discharge pressure by using variable speed drive (VSD) motors.

Optimization of current units to achieve the targets is an effective tool that saves cost and time both and this technique enables to use the current asset potentials and it also plays a vital role and helps exploration & production companies for making correct procurement decisions for new equipments. (Classic Corporation)

1.2          RESEARCH AIMS AND OBJECTIVES

1.2.1        General Objectives

• This research is to bring out the various factors involved in selecting an artificial lift system for oil production optimization.

• To come out with advantages and disadvantages of this artificial system over one another.

1.2.1       Specific Objectives

Once we start the oil production stage and the oil starts to flow into the wellbore but we aim to lift the reservoir fluid (oil) to the surface this can be achieved in the presence of high pressure.

Once the Pdf (flowing well pressure ) is not high enough to keep the hydrocarbon flow in a single phase in other words the gas which was dissolved in the oil will evolve resulting in liquid hold up, as we get closer to the surface the gas phase will take over the well leaving the liquid phase behind, as this stage is reached the well must be supplied with energy to support Pdf so that we will be able to produce the oil which was held up, to do so we can use one of the methods of artificial lifting.

In Our project we will be talking about the gas lift in particular and our main objectives will be detecting variations in production rates as we implement gas lift artificial lifting in one of the wells of northern Iraq fields, we will also answer the questions of which gas must be used? What is the optimum volume? What is the most suitable flow rate? With considering the depth and to finalize our project we will model it using prosper software.  

1.3         PROBLEM STATEMENT

Over time, it is the advent phenomenon that the water cut in production tubing will increase due to the injection of water for pressure maintenance of the reservoir and completion using the aid of gas lift process will surely face problem in this scenario. These problems will result in lower flow rates of oil which will make the gas lift process ineffective.

The problems that need to be addressed and solved include:

• Increased injection rates of lift gas are required because of the increasing hydrostatic head of the column of the fluids present in the tubing that consists of oil and water so more volume of lift gas is required to achieve maximum production. This lift gas injected rate should be optimum because injection more from an optimum rate will cause a decrease in production due to the gas slippage effect. Therefore the lift gas requirements need to be recalculated to achieve maximum production by choosing the accurate and optimum injection rates.

• How to optimize the compressor unit to accommodate the increased injection rates of lift gas that is essential to lift the fluid from the well at economically optimum rates and at the same time maintains the pressure of the lift gas which should be sufficient for an effective gas lift process. Optimization of gas lift operation must be acceptable which implies that the difference between the total power requirements at design capacity and optimized conditions should be in acceptable ranges.

1.4.          RESEARCH QUESTION

• What is the goal of a gas lift in a pressure depleting well?

1.5 Limitations of Gas Lift

The primary limitation for gas lift operations is the lack of formation gas or an injection-gas source. Wide well spacing and lack of space for compressors on offshore platforms may also limit the application of gas lift. Poor compressor maintenance can increase compressor downtime and add to the cost of gas lift gas, especially with small field units. Compressors are expensive and must be properly maintained. Generally, gas lift is not as suitable as some other systems for single-well installations and widely spaced wells. The use of wet gas without dehydration reduces the reliability of gas lift operations