Type: Process Essays
Sample donated: Bernadette Wallace
Last updated: September 16, 2019
Liquid droplets that load ingas wells result in several serious issues. To solve these problems, differentlifting method were developed. Lifting system that are used now for horizontalgas well were originally developed for oil wells. Moreover, this research istargeted mainly toward gas well deliquification (remove liquid loading fromwellbore or dewatering).
In natural gas well, theproduced gas particles are attached to a load of liquid droplets (oilcondensate or water). Moreover, the produced gas can lift liquid droplets tothe surface at the early stage of the production when the gas pressure is highenough to provide such critical velocity to carry the liquid to surface. After period of production when the wellbecome mature, an amount of liquid that present inside the tubing along withgas produced result in disperse within gas that drag gas flow downward bygravity. Therefore, gas velocity falls and leads to extra decreases in extractedliquid volume that cause accumulation which rise the burden of the ability tocarry up liquid droplets, which lead to gather more liquid and extra builds upaccumulation of liquid that cause a reduction or complete stop of the gasproduction. · To discuss the improvementin deliquification.
· To discuss new designmethod of lift system. I collected the data for aresearch in Well completion course that is about summarizing some latest improvementin lifting in gas wells. Moreover, I collected data using OnePetro website fromdifferent journals and SPE papers. The main methodology that I followed is toexplain the main difference between lift systems and to summarize a real gaswell case that undergoes different lifting technique.
Gas well deliquification orgas well dewatering is a method of lifting that used to get rid of liquid (oilcondensate or water) that occur within gas during production from gas well. To deliquefyliquid in well, there are different possible solutions such as:· Natural flow.· Compression.
· Gas lift.· Beam lift.· Plunger lift.· Foam lift.However, it must be careful that the gasvelocity is affected by the design of the well bore (such as suddenexpansion/contraction). Moreover, the gas condensate is affected by the rate ofproduction.
In other words,The slower the velocity => the poorer thelift => the longer the transit time => the more heat is lost => watercondensate and start to load.Therefore, this research is directed andfocus on foam injection that is used to increase gas production along with gas lifting.The foam performance depends on different parameters such as pressure,temperature, hydrocarbon fraction, and foamer agitation velocity. In addition,Foam Assisted Gas Lift may be used, and it is an economicalchoice due to its increased gas production rate and it requires less injectedgas. Before injecting the foam, there are three types of tests that applies onfoam to test its performance underground that are:· Foam buildup test.
· Collapse test.· Liquid carryover test. In addition to that there are system consideration thatcontrol the validity of lifting solution such as:· Cost of production andamount of pay.· Solution life.· CO2 and H2S corrosion.· Acid resistant.
· Amount of water and theability to control it.· The cause and depth ofcondensation.· The power required.· The costs and risks ofworkover.
Some of the methods are depend on rechargingthe well from near formation Recharging from low permeability zones to higher permeablezone. In methods such as:· High permeability streaks.· Natural fracture.· Stimulated fractures. Nevertheless, liquid behavior is affected bythe deviation of the well, where in the vertical well, all the liquid dropletsare lifted by flowing gas.
However, in a deviated well, a separation ispossible due gravity where liquid droplets will be accumulating down hole at anangle. However, the proposed gas wellcase is vertical well and it undergoes these methods: The method of gas lift isused to improve the production rate and to deliquefy the gas well as anartificial lift technique by decreasing the hydrostatic pressure of the liquid.This method is applied by injecting high pressure gas in the well pipe throughvalves on the annulus string. Foam assisted lift is a newtechnique that is used to dewater the gas well by decreasing the liquid surfacetension and its density. This method depends on injecting soap from surface inthe tubing through capillary string.
Moreover, the system components are:· Capillary soap· Stainless steel capillarystring· Foot valve (soap injectionvalve)· Capillary hanger· Soap pump · Soap tank Andthe systematic process of Foam assisted lift is simplified in the following graph: It is a hybrid technique that useboth Gas lift and Foam assisted lift to improve the effectiveness of the two methodsby injecting soap and gas. In other words, the soap is increasing the liquidcolumn and the injected gas energize the flow. This method is most effectivewhen:· The well flow is very low,and much liquid was accumulated· The liquid column is lowerthan gas valve.This is the example ofnatural flow gas well that well be focused on in this research paper and itsrecovery technique was changed three times after depletion. The followingfigures show main information about the proposed gas well in it productionprofile.
(Tayyab, 2016)The cumulative productionafter perforation of Sand Y is around 18 MMMCF and around 1 MMSCFD initiallythat is increasing with time and loads in the tubing. After 8 years ofproduction, the flow rate of gas fall to 1 MMSCF per day and the Water-Gasratio was 300 STB/MMSCF. Therefore, Sand Z was perforated to comminglallyproduce around 7 MMSCFD. Moreover, wellhead gas compression systems was appliedfor 10 years to rise flow up to 12 MMSCFD and 30STBMMSCF of Water-Gas ratio. In2011, the was depleted due to loss of energy to flow the gas with around 57%recovery rate. The Gas lift system wasintroduced in M-1 well in 2012 to deliquefy the gas well by inject 0.
4 MMSCFDof gas the produced around 1.7 MMSCFD and 225 STBD of water. Shortly, the gasflow dropped to 1.2 MMSCFD with larger Water-Gas ratio that show liquiddroplets are loading in the tubing. After 6 Months, Gas lift system hasproduced only 1.6 BCF that is 2.4 % recovery. After Gas lift system wassuspended, a Foam assisted lift was introduced in the gas well.
Soap wasinjected close to the perforation using capillary string. In the beginning ofinjection, Soap was injected at rate of a half-gallon per day and raisedgradually to a rate of 5 gallons per day that result in 1.5 MMSCFD of gas.However, any further increment of injected soap leads to drop in the productionrate.
After three months, a liquid droplets load occurs and requires gas liftto provide sufficient energy to flow the gas well. Therefore, new liftingsystem were introduced in the well. One of limitation of foam that is affectedby temperature. After 5 months in 2013, acombined system of Gas lift and Foam assisted lift was applied to dissolve theliquid loading of the gas well. In fact, it was a challenge to determine theoptimum rate of soap and gas injection rate at that time because there were nostandard values for this combined system.
Therefore, several trial and errorwere applied and the best values for M1 well were 2 Gallon per day of soap and0.3 MMSCFD of injected gas. After 21 days of instable production, the productionstabilizes at 1.3 MMSCFD with 300 BBL of water per day.This a table shows anefficiency of each system that has been used in this gas well over four yearsof production after depletion of natural flow and liquid loading occurrence: (Tayyab, 2016)It Shows that Foam assisted gas lift providesmost profitability per year of 3.
0 $MM/year. In contrast, Gas lift and Foamassisted lift achieve 1.6 $MM and 1.5 $MM of profit per year respectively. Conclusion· It is advantageous to use acombined system of Gas lift and Foam assisted lift that optimize productionrate of gas well and overcomes limitation of two methods alone.· Soap injection has anoptimum rate; any variation affects the production negatively.· High temperature reduce theeffectiveness of Foam performance.