# Presentation: 198674

## Lessons Learned 
from Natural Gas STAR

Offshore Technology Transfer Workshop

Shell, GCEAG, API, Rice University and
EPA’s Natural Gas STAR Program

June 8, 2004

**from Natural Gas STAR**
**Offshore Technology Transfer Workshop**
**Shell, GCEAG, API, Rice University and**
**EPA’s Natural Gas STAR Program**
**June 8, 2004**

**Minimizing Methane Emissions from Glycol Dehydrators**

## Minimizing Emissions from Glycol Dehydrators: Agenda

- Methane Losses
- Methane Recovery
- Is Recovery Profitable?
- Industry Experience
- Discussion Questions

## What is the Problem?

- There are ~ 38,000 glycol dehydration systems in U.S. production sector
**Estimate 350 glycol dehydrators in GoM**
- Glycol removes moisture from produced gas
**Also absorbs methane, VOCs and HAPs**
- Glycol reboilers vent absorbed water, methane, VOCs, HAPs to the atmosphere
**Wastes gas, costs money, reduces air quality**

## Basic Glycol Dehydrator System Process Diagram

**Basic Glycol Dehydrator System Process Diagram**

**Glycol Contactor**

***Dry Sales Gas***

***Inlet Wet Gas***

***Lean TEG***

**Pump**

**Driver**

***Water/Methane/VOCs/HAPs***
***To Atmosphere***

***Rich TEG***

***Fuel Gas***

**Glycol Reboiler/ Regenerator**

**Gas Bypass**

**Glycol Energy Exchange Pump**

**Notes:**
GMAQS study indicates that the reboiler often uses electric heater or waste heat

## Glycol Dehydrator Methane Emissions

- Absorbed plus bypassed methane is vented by reboiler
- On average, 600 Mcf methane per glycol dehydrator emitted each year
- To date, ~ 13.5 Bcf methane has been saved in U.S. operations with optimized glycol circulation, flash tanks and electric pumps

## How Can Glycol Dehydrator Emissions Be Minimized?

- Optimized glycol circulation rates
**Methane emissions are directly proportional to glycol circulation rate**
- Flash tank separator (FTS) installation
**Recovers all methane bypassed and most methane absorbed by glycol**
- Electric pump installation
**Eliminates need to bypass gas for motive force; eliminates lean glycol lean contamination by rich glycol**

## Optimizing Glycol Circulation Rate

- Gas well’s initial production rate decreases over its lifespan
**Glycol circulation rates designed for initial, highest production rate**
- Glycol overcirculation results in more methane emissions without significant reduction in gas moisture content
**Natural Gas STAR partners found circulation rates two to three times higher than necessary**

## Overall Benefits

- Methane savings
- Reduced emissions of methane, VOCs, HAPs
- Lower operating costs
**Reduced glycol replacement costs**
**Reduced fuel costs**
- Immediate payback
- No footprint changes

## Installing Flash Tank Separator

- Most dehydrators send glycol/gas mixture from the pump driver to regenerator
- Flash tank separator operating at fuel gas system or compressor suction pressure recovers ~ 90% of methane
**Recovers 10 to 40% of VOCs**

## Installing Flash Tank Separator

- Flashed methane can be captured using an FTS
- Many units are _not_ using an FTS

## Overall Benefits

- Gas recovery
- Reduced methane emissions
- Low capital cost; short payback period

- Flash Tank

**Gas Recovery**

**Reduced Emissions**

**Low Capital Cost/Quick Payback**

## Decision Process for Installing Flash Tank

** ****IDENTIFY destination for low pressure gas**

**ESTIMATE capital and installation costs of flash tank**

**IDENTIFY dehydration units w/o flash tanks**

**ESTIMATE gas savings potential**

**CONDUCT economic analysis**

**DETERMINE footprint feasibility**

## Flash Tank Applications

- Flash tanks are a long-term solution
- Flash tanks require a low pressure gas sink
**Fuel gas line**
**Compressor suction**
- Standard footprints
** **

## Flash Tank Costs

- Two elements: capital and installation costs
**Capital costs range from $5,000 to $10,000 per flash tank**
**Installation costs range from $2,400 to $4,300 per flash tank**
- Negligible O&M costs

## Installing Electric Pump

- Gas-assist pumps require additional wet production gas for mechanical advantage
**Removes gas from the production stream**
**Largest contributor to emissions**
- Gas-assist pumps contaminate lean glycol with rich glycol
- Electric pump installation eliminates motive gas and lean glycol contamination
**Economic alternative to flash tank separator**
**Requires electrical power**

## Overall Benefits

- Financial return on investment through gas savings
- Increased operational efficiency
- Reduced O&M costs
- Reduced compliance costs (HAPs, BTEX)
- Similar footprint as gas assist pump

## Decision Process for Installing Electric Pump

** ****DETERMINE footprint feasibility**

** ****ESTIMATE capital, installation and O&M costs**

**DETERMINE availability of electrical power**

**DETERMINE electric pump size**

**ESTIMATE value of gas saved**

**CONDUCT economic analysis**

## Economic Analysis

**Three Options for Minimizing Glycol Dehydrator Emissions**

## Partner Reported Experience

- Partners report cumulative methane reduction of 13.5 Bcf since 1990
- Past emission reduction estimates for U.S offshore is 500 MMcf/yr or $1.5 million/yr

## Case Study

- One partner routes glycol gas from FTS to fuel gas system, saving 24 Mcf/d (8,760 Mcf/yr) at each dehydrator unit
- Texaco has installed FTS
**Recovers 98% of methane from the glycol**
**Reduced emissions from 1,232 - 1,706 Mcf/yr to <47 Mcf/yr**

## Lessons Learned

- Optimizing glycol circulation rates increase gas savings, reduce emissions
**Negligible cost and effort**
- Flash tank separators reduce methane emissions by about 90 percent
**Require a gas sink and platform space**
- Electric pumps reduce O&M costs, reduce emissions, increase efficiency
**Require power source**

## Discussion Questions

- To what extent are you implementing these technologies?
- How can the Lessons Learned study be improved upon or altered for use in your operation(s)?
- What are the barriers (technological, economic, lack of information, regulatory, focus, manpower, etc.) that are preventing you from** **implementing this technology?