thesis new

An investigation the effect of well types and their geometry on production of southern Pars gas field using

Nodal Analysis

supervisors: Prof. Ali Moradzadeh

Dr. Peyman Pourafshary

Presented By: Farhad Orak

Shahrood University of TechnologyOctober 2012 1

Shahrood University of Technology

Production Optimization using Nodal Analysis

Effect of Well Geometry on Production of Field Case Study

Field Geography Situation & Geology

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5 Results & Recommendations

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An investigation the effect of well types and their geometry on production of southern Pars gas field using Nodal

AnalysisApplication of Multilateral Wells in HC Reservoir

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GeologyMultilateral Wells

Production Optimizatio

nWell

Design

Advantages

Disadvantages

Risks

Benefits

• Higher productivity indexes(PI).• Relatively thin layer drainage can be

accomplished(0.8m). • Decreased water and gas conning. • In secondary and EOR applications, long

horizontal injection wells provide higher injectivity rates.

• In heterogeneous reservoirs, more oil and gas pockets can be exploited and an increased number of fissures can be intersected.

• It definitely helps to reduce the drawdown that is experienced on a single lateral leg

• High risk associated to drilling and completion may take away the economic benefit.

• Remotely operated inflow valves to control flow rates from well branches and zones.

• Debris when milling through casing in existing completions.

• Highly sensitive to heterogeneities and anisotropies (both stress and permeability).

• Very complicated drilling, completion and production technologies are used.

• Interference of well branches may occur (Cross flow may take place).

• Borehole instability • Stuck pipe • Drilling formation damage • Staying in the productive

zone • Casing exit orientation • Whipstock orientation in

existing wells

• Horizontal multilateral completion allows the placement of the junction in the reservoir, reducing overburden drilling, casing and cementing costs.

• These cost savings are in addition to the service capital expenditure costs (structures, wellheads, pipelines) and operating expenses.

Where these types of completions make sense:• High-cost drilling markets (such as offshore or

deep reservoirs)• plays where increased reservoir exposure is

required (such as heavy oil)• areas where geological structures produce

segregated reservoir targets.

Results

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GeologyProduction Optimizatio

nWell Design

geography Situation

Results

South Pars gas field is located in Persian Gulf and known as the largest gas field in the world, which has the 50% of entire Iran Gas supply and 8% of the world. It is also extended into Qatar territorial water where it is called the North Field.

Multilateral Wells

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Geology


nWell Design

Reservoir geology

Results

It consists of four producing gas layers K1, K2, K3 and K4 which are separated by anhydrite layers.

Reservoir thickness is about 400 meters. The thickness of each layer is different with others.

This reservoir is constructed of Kangan and Dalan formations with Lithology of lime stone, dolomitic Lime stone, Anhydride and staked clay in the depth of 2700 meters.

More of the gas reserves are in Kangan and Dalan formations which are the main layers of South Pars Gas Field, there are also other layers which Oil existence in those layers are approved according to performed drilling .(Darian)

Multilateral Wells

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Geology


nWell Design Results

Challenges

The ordinary trajectory of wells in this field is a 42˚ slant path that touches all of these layers and it culminates in a commingled production after all.

But problem arises here, on the flanks, where the level of WGC is too high that K3 and K4 are inundated with water, and there is no enough production from this two layers, then it calls for finding another way to extend the production period.

In this case the role of multilateral wells becomes highlighted and those conventional wells can be substituted by their novel multilateral forms.

Multilateral Wells

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Multilateral Wells Geology


nWell Design

Well Design

Results

Start Select Model Options

Set up and Match PVT

Model

Input System Equipment &

IPR

Yes

Match IPR & VLP

Calculate System

Sensitivities

Performance

Acceptable?

No Review DesignFinish

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Procedure which is used in PROSPER:


Production Optimizati

onWell DesignResults

Multilateral Well (Quadrilateral )

Advantages:• Decreased water

conning.• Expose a greater

section for completion• Steady & Stable

ProductionDisadvantages:• High Cost & risk

associated to drilling & Completion

• Moderate production rate 8



onWell Design

Results

IPR Plot IPR & VLP Plot

81.232 MMscf/day

Well deliverability is determined by the combination of well inflow performance and wellbore flow performance.This work focuses on prediction of achievable fluid production rates from reservoirs with specified production string characteristics.The technique of analysis is called ‘‘Nodal analysis’’ (a Schlumburger patent).

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onWell Design

Results

Dual Opposed Multilateral Well IPR Plot

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Production Optimization Results

Well Design Production

OptimizationNodal

AnalysisTo simulate the fluid flow in the system, it is necessary to ‘‘break’’ the system into discrete nodes that separate system elements (equipment sections). Fluid properties at the elements are evaluated locally.Nodal analysis is performed on the principle of pressure continuity, that is, there is only one unique pressure value at a given node regardless of whether the pressure is evaluated from the performance of upstream equipment or downstream equipment.The performance curve (pressure–rate relation) of upstream equipment is called ‘‘inflow performance curve’’;the performance curve of downstream equipment is called ‘‘outflow performance curve.’’ The intersection of the two performance curves defines the operating point, that is, operating flow rate and pressure, at the specified node.

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FLOW

GeologyMultilateral Wells Well Design

Production Optimization

Results

Used Procedure

1. Determine which components in the system can be changed. Changes are limited in some cases by previous decisions. For example, once a certain hole size is drilled, the casing size and, therefore, the tubing size is limited.

2. Select one component to be optimized ( in this work focus is on production pipe diameter, well head pressure, skin effect and produced water effect).

3. Select the node location that will best emphasize the effect of the change in the selected component. This is not critical because the same overall result will be predicted regardless of the node location ( in this work the node is assuming at the well end and a the above of lateral branch).

4. Develop expressions for the inflow curve and outflow curve (As plotted).

5. Determine the effect of changing the characteristics of the selected component by plotting inflow curve versus outflow curve and reading the intersection (As plotted).

6. Repeat the procedure for each component that is to be optimized.

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Results

IPR & VLP Plot Before Optimization

Well Design

Multilateral Well(Dual Opposed )Q= 97 MMscf/day

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Results

Effect of tubing size

Q:

3.95": 79 MMscf/day4.78": 91 MMscf/day6.18": 104 MMscf/day

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Results

Effect of Wellhead pressure

Q:

2500 Psi: 76 MMscf/day2000 Psi: 94 MMscf/day1500 Psi: 101 MMscf/day

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Results

Effect of water cut

Q:

0% : 97 MMscf/day40% : 80 MMscf/day

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Results

Skin Effect

Q:

+1 : 114 MMscf/day+7 : 84 MMscf/day

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Results

After optimization

Specifications:Tubing size: 6.18 inchWellhead pressure: 2000 psi

114.324 MMscf/day

Assumptions:Water Cut: 5%Skin Factor: +1

Q in comparison with pre-optimized: +17 MMscf/day 18

GeologyMultilateral Wells Well Design Production

Optimization Results

Results

1. According to small ratio of Kv/Kh , it’s not suitable to drilling the horizontal branches in this field although it’ll be more reservoir exposure . So drilling of slant branches (Dual opposed multilateral wells) has the better efficiency.

Results

2. During the production, chosen well with tubing Size of 3.95" and 4.78" causes restriction because of tubing. But the production rate increases at the production with tubing Size of 6.18".

3. According to production potential of the well and reservoir and Capacity of surface equipment Wellhead Pressure 2000 Psi for Dual Opposed Multilateral Well is Appropriate.

4. If the creation restriction in bottom hole completion or Formation damage, inflow performance can be Improve using the Work Over Such as Hydraulic Fracturing or Acidizing.

5. According to formation stability (type and structure of reservoir rock), completion by the method of open hole is appropriate and there’s no need to mechanical integrity in the junction.

6. To avoiding of Cross flow in design of multilateral well, One-way Chock usage can lead to increasing of Reliability in completing design.

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GeologyMultilateral Wells Well Design Production

OptimizationResults

Recommendations

1. Considering the limits in production on the flanks (where the level of WGC is too high that K3 and K4 are water invited), it’s suggested to use of multilateral wells with horizontal branches and utilization of intelligent equipment's in reducing of water production and reducing of Cross flow risqué and better and optimized production of these zones.2. Investigating of optimum length of horizontal branches and drilling appropriate angle for more reservoir exposure.

3. Estimation of reservoir depletion time in different production condition with reservoir simulation.

4. For more control during production and selective production from zones, it’s suggested to use of PVT gauges and SSD in design of bottom hole equipment.

5. Above all, this study can be done for the great gas field that just explored in the deep waters (712 m) in Caspian Sea.

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Thanks for your attention !

Questions?

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