SURPRISING TEST RESULTS

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- -A

Geopress 1980 and

ured-Geothermal T a - t i n g of Five "Dry Holes" During

.

1981.

- 3

By: R i c h a r d Z. K l a u z i n s k i , Eaton O p e r a t i n g Company, I n c .

t3CopyrlQhl1681. Soclety of Petroleum Enplnwrr of AIME

This paper was presented at the 58th Annual Fall Technicel Conference and Exhlbltlon of the Society of Petroleum Enplneers of AIME. held In S 8 n Antonio, Texas, Oclober 57.1981. The material I5 iubject Io Correctlon by the author. Permlsslon to copy Is reslricted lo an abstract 01

not mor. than 300 words. Write: N. Central Expressway, Dallas. Texas 75206.

This paper summarizes the testing of five hot, geopressured aquifers in different geologic environments in .Texas and Louisiana by Eaton Operating Company for the

U.S. Department of Energy.

The results w e r e encouraging. Natural gas-to-brine content ranged from 33.0 to 55.0 SCF/bbl. Gas production rates ranged from 93 to 600

MCFD.

Sustained water production rates ranged from 1,950 t o 15,000 BWPD.

Bottom-hole temperatures ranged from 260 t o 327OF. Res- ervoir pressures ranged from 6,627 psia t o 13,203 psia. A test near Beaumont resulted in discovery of oil and gas.

INTFt0DUCN)N

haeasing demand for exploration and development of domestic energy resources has led t o a re-examination of 'unconventional. gas BOUCCS which are currently cate- gorized by industry as 'not practical' or 'too costly.' One of these sources currently being investigated is the geopressured-geothermal energy potential of the Gulf Coast Basin formations. Substantial quantities of recoverable gas, along with fluid heat and hydraulic energy, are esti- mated t o exist in geopressured zones.

T h e

magnitude and economic potential of these geopressured-geothermal re-

sources is under investigation by the US. Department of

Energy, with willing cooperation from the petroleum indus-

trlr.

THE

WPJS

OF

O P F O R T U ~ PROGRAM

This paper discusses the continuing

DOE

"Wells of Opportunity' testing program and specifically covers the period from May 1980 t o August 1981, during which five industry 'dry holes' were completed and tested by Eaton Operating Company for the

DOE.

The 'Wells of Opportun- ity' program w a s initiated in 1977 t o take advantage of wells drilled by industry in search of oil and gas which zue found t o be unproductive and which can be completed in geopresrured reservoirs. The program provides short-

References and Illustrations a t end of paper.

term test data on the energy-producing potcntial of underground aquifers along the Gulf Coast of Louisiana and Texas and reduces present uncertainties associated with reservoir and fluid characteristics. Completing these wells in the zones of interest allows testing them a t lower costs than by drilling new ones. These wells, and the wells tested under this program, however, are generally not in favorable geologic structural locations for production of high volumes of fluids.

The short-term testing provides information con- cerning the following:

The aquifer fluid characteristics, including hydrocarbon content and solubility, chemical composition, and physical properties.

The near-wellbore characteristics of geopressured- geothermal reservoirs, including pressure, temperature, permeability, porosity, extent and distribution of rands and shales, rock composition, aqdfer geo- metry, and distance to boundaries.

The

behavior of reservoir and fluids under conditione of fluid production, including formation flow capa- d t y , well deliverability, pressure/time behavior a t different flow rates, and other information related t o the reservoir production drive mechanism and physical and chemical changes that may occur with vari- o w production conditions.

The evaluation of completion techniques and production strategies for geopressured-geothermal wells, including the performance of downhole and rurface equipment, scaling and corrosion potential, formation rand production potential, and brine disposal meth-

OdS.

0

SURPRISING

TEST

RESULTS

The Louisiana test sites were near Lafayette, Lake Charles,

and

Baton Rouge. The Texas test locations were near Beaumont and Laredo. Table 1 lists reservoir informa- tion determined during testing. Table 2 summarizes some of the chemical and physical data obtained.

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SPE 10280 GMPRESSUREDGEOTKERMAL TESTING OF €WE

P R Y HOLES'

DURING 1980 AND 1981

Two 'Wells of Opportunity' tests prior t o 1980 indi- cated gas-to-brine content of 22.8 and 24.0 SCF/BBL. The gu-to-brine ratios in the five wells discussed here were considerably higher. They ranged from 6 low of 33.0 SCF/bbl in the Baton Rouge test t o a high of 55.0 SCF/bbl in the Lake Charles well. Actual gas production rates ranged from 93 t o 600 MCFD. The Laredo Wilcox sand and the Lake Charles Hackberry sand contained gas consider ably in excess of solubility in the brine. The Baton Rouge Tuscaloosa reservoir, however, appeared t o be undersatur 6ted with gas. Testing low-salinity aquifers is the main reason for finding improved gas-to-brine ratios. Gas mlubilities in brine increase with lower salinities, higher temperatures, and higher pressures.

The short-term reservoir pressure drawdown and buildup tests did not define all reservoir limits. All of the q u i f w , however, appeared t o be restricted by permeability barriers in the form of sand pinch-outs, or faulting, or both. Actual sustained production rates w e r e lower than expected, ranging from a low of 1,950 BWPD in the Laredo w e l l t o a high of 15,000 BWPD in the Lafayette test.

These flow rates would be considered excellent for hydrocarbon production but are not presently considered eco- nomical geopressured-geothermal energy production rates.

The Beaumont Yegua sand test resulted in the acci- dental discovery of a commercial oil and gas well, which was recently producing 1.7 MMCFD and 150 BOPD. Exten- sive testing and saltwater production considerably reduced the reservoir pressure, inducing an 'attic' oil and gas production situation by allowing updip hydrocarbons t o expand down into the test perforations.

Actual measured bottom-hole temperatures were from 7% to 16% higher than had been calculated from open-hole log data. The Baton Rouge well was the hottest, with 6 temperature of 327oF. Some actual water salinities were significantly different from log-derived numbers.

Considerable amounts of sand, formation clays, and carbonate precipitates were produced from a l l of the wells.

Solids production was not expected from the formations being tested. The high flow rates which caused local drawdown around the restricted wellbores probably intensi- fied total solids production from zones which would no- mall7 not be sand producers.

-e Laredo Wilcox reservoir and the Baton Rouge l b c d o o s a zone contsined unexpectedly high amounts of carbon dioxide in the flare line gas. The upper values of C 0 2 content w e r e 22.6 and 26.4 mole percent, respect- ively. T h e L d a y e t t e Frio well, however, produced a gas which contained over 91% methane.

Scaling and corrosion of the test equipment w a s wprkdngly light. The relatively low salinity of the brines contributed to this.

COMPLETION TECENIQUES

The test well completion methods are fairly uncom- plicated. Tbe formations t o be tested are conventionally cased off and cemented. The tubular configuration is one in which fluids are produced either through large diameter (3K-inch) tubing set on 6 packer or through a casing-tubing annulus where small diameter (2-3/8 inch) tubing is installed h i d e larger (5K-inch) casing, without a packer.

Figures 1 and 2 are rchematics of typical tubular configur ations. The annular flow configuration has four advantages over the tubing flow completion: 1) the wireline and tools, such as the downhole pressure gauge, are not exposed to the hostile environment caused by flowing fluids, 2) the well can be efficiently killed in an emergency simply by circulating heavy mud down the tubing and up into the annulus, 3) chemical inhibitors can be easily injected near the perforations through the tubing, and 4) dat6 on fluid friction loss can be obtained, along with information on flowing bottom-hole pressure versus surface tubing pressure. The disadvantage is that the casing string must be designed for full well pressure and has to be carefully handled. This can increase the cost of a completion. T h e casing is perforated with all tubulars in place and with a hydrostatic pressure inside the casing lower than the reservoir pressure. (The "differential" perforating techni- que reduces problems associated with plugging of p e r f o r ations with drilling mud and perforating debris). The ef- fects of tubular elongation (due to temperature) and bal- looning (due to pressure) are considered in the tubular design program.

c m A s T R E E s

Two types of Christmas trees are used, depending on type of flow desired. Figures 3 and 4 are schematics of the two types of Christmas trees. The tubing-flow tree incorp- orates an upper section where two 3-inch flow loops come off a split-flow body. A 'swab' valve is installed on top for wireline accessibility. All valves in the upper section are 3-1/6 inch ID. Fail-safe automatic nafety valves are illustrated in both figures. In the annulwflow tree, produced fluids exit through two outlets in the tubing head.

Two sections of 3-inch pipe connect the tubing head outlets to a common 'Y' block near the tree. The upper section consists of a

'T"

arrangement, allowing wireline accessibility, and a side port to allow pumping operations even while a wireline is in the hole.

DISPOSAL WELLS

Disposal wells are completed very simply. Typically, SH-inch casing is set and cemented through the zones of interest (3000 to 6000 feet).

No

tubing is used. Wells are perforated after mud has been removed. In most cases 6cid is required to obtain a well capable of accepting all anticipated production from the test well at a pressure below 500 psi. The completion methods used have been formulated with efficiency and low cost in mind rather than 6 long-term disposal operation. The quality of the disposal water is the most important factor controlling the success of disposal operations. Sand control of the uncon- solidated disposal sands is probably the second most i m p o r tant factor.

SURFACE l"G FACIUTTES

The test facilities are designed to measure, process, Design and dispose of the well effluent continuously.

criteria are generally as follows:

a Wellhead Working Pressure 10,000 psi a Flow Line Shut-In Pressure

alooo

psi

a Temperature 350'

F

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RICHARD

z

KLAUZINSICI 3

e BrineFlow Rate 20,000 BPD

0 Separator Operating Pressure 1,200 psi

0 Filter Operating Pressure

e Resistance to Hydrogen Sulfide Yes

Figure 5 is a diagram of the surface test equipment.

Most of the equipment is rkid-mounted for easy assembly and transportation. The w e l l stream enter. the flowline at the point where the two flow loops connect to a 'Y' block.

The pressure, temperature, and flow r a t e (of water and gas) are measured ahead of the choke manifold. Effluent aamples are obtained from the rampling block, which contains a %inch diameter tube that protrudes into the flow stream. Steel fin-type miring blader (turbolizerr) are located ahead of the sampling tube.

The

chemical inhibitor injection point is located downstream of the rampling tube and upstream of the choke manifold. Flow r a t e and pressure drop are con- trolled at the choke manifold by two adjustable chokes.

The fluids then enter a data header at a lower pressure.

T h e data header incorporatea a sonic sand detector and

~cale/corrosion-measuring coupons. T h e main flow then enters a conventional horizontal 3-phase separator.

The

gas leaving the separator is measured by an orifice meter and then flared. The brine pasres through a Uquid- metering skid. The skid is composed of two 3-inch turbine meters and two pneumatically operated brine flow discharge ralver. T h e manifold is derigned ro that the turbine meters can be separately calibrated at any time during testing. Two 110-barrel tanks and a pump are used t o check the turbine meters.

The.brine leaving the water-metering skid passes through a filtering d t before entering the disposal well.

Pressure and temperature are measured at the dirposal wellhead. Separator discharge pressure is usually maintain- ed at a higher pressure than the surface disposal well injection pressure. Tbia eliminates the need for costly dirporal pumps.

The foliowfng data ia digitally recorded when possible during testing.

Bottom-hole pressure e Surface tub- preasure s Surface annulus pressure

Wellhead temperature e Wellhead effluent flow rate e Sonic rand detector output e Separator pressure

0 Orifice meter differential pressure e Gar temperature

e

e Filter differentid pressure

Separator brine &charge volume and rate

e

e Disporal well surface temperature Disposal well rurface injection pressure

Final reports konfahing all of the above data, along with analysis and conclusions are prepared after each well is tested. These reports can be obtained from the DOE.

CONCLUSIONS

1, Comparison of produced gas-to-brine ratios with the recombination studies of separator gaa and water indicate that

in

most cases the formation waters are at least saturated. It is quite possible, however, that as this program continues we will find that many aquifers are either supersaturated or undersaturated with gas.

2. Geopressured-geothermal (CEO? energy, as a by- product of industry 'dry holes," warrants further investigation by industry. A "dry hole" or a depleted producing well may have the p t e n t f a l to become an economical gas source. A GEO disposal well might serve as a convention- al injection w e l l in fields where shallow pressure mainten- ance projectr are underway.

3. With a few modifications, conventional petroleum industry production equipment is adequate for processing produced fluids. Some gas, generally 1 t o 5 SCF/bbl, does remain in the disposal water, but this gas is high in COz content and is not usable. An automatic self-cleaning 5*

micron filtering system appears t o be very effective in providing good disposal water quality with little mainten- ance.

4. The state of the art of deriving water salinity from logs needs improvement. The ability to accurately calcu- late water salinity is important in estimating gas sat- ation in geopressured-geothermal wella, and i t can be critical

in

evaluating hydrocarbon content of potential oil and gas reservoirs.

5. All other parameters being equal, low salinity aquifers contain more gas, and they are less troublesome t o produce because of reduced carbonate rcaling.

ACKNOWLEDGEMENTS

I wish to thank Eaton Operating Company, trc. and the

U.S.

Department of Energy for their permission to use and publish the data in this paper. I also acknowledge the assistance of

Mr. John

Holderness in the preparation of the manusaipt and exhibits.

REFERENCES

1. Bassiouni, 2. and Silva,

P. 'A

New Approach t o the Determination of Formation W a t e r Resistivity from the

SP

Log," SPWLA, The

LOR

Analyst, June, 1981.

2. Blount,

C.W.;

Price, L.C.; Wenger,

M.M.;

and

T d o , M.

'Methane Solubility in Aqueous NaC1 Solutions at Elevated Temperatures and Pressures,' Progress Report, August 1,1979, DOE Grant

NO.

ET-78-S-07-1716.

i

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* 4

- _

G E O P R E S S O R H ) - C E A L TESLeJG OF

FLVE

'DRY BOLES' DURING 1980 AND 1981 SPE 10280 3. Cor,

W.R.

'Key Factors Affecting Landing of Cas-

ing,' Am Southwestern District Committee Study on Cas- ing Landing Practices, Shreveport, Louisiana, 1957.

4. Dunlap, H.F., 'Study of Log-Derived Water l e d s t i r - ity Data in Geo Formations,' Center for Energy Studies, Sixth Progress Report, August 1980.

5. Dunlap, H.F., *Studies of Log-Derived Water Resis- tivity Data

in

Geo Formations: Center for Energy Studies, Twelfth Progress Report, February 1981.

8. McCoy et al, 'Preliminary results of the Wells of Opportunity Geopressured-Geothumsl Testing Program,' SPWDOE 8958, presented at the Unconventional Gas

Re-

covery Symposium, May 16-20, 1980, Pittsburgh, Pennsyl-

V m i &

9. Division of Geothermal Energy, Assistant S e a e t a r y for Resource Applications, Department of Energy,

"Re-

search and Development Program Plan for Geopressured- Geothermal Resources,' December, 1980.

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TYPICAL ANNULAR FLOW COMPLETION

A

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k 13 3/8" SURFACE CAS1 NG

AT 3500'

9

9 5/8" INTERMEDIATE CASING

AT 12,000'

L

7 5 / 8 " L I N E R AT 14,000'

23f8" T U B I N G AT 14,900' PERFORATIONS AT 15,000'

51/2" PRODUCTION CASING AT 15,500'

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Figure 4

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SURFACE SAFETY VALVE 2" 5,000 P S I W.PI

5.000 P S I W.P.

CASING HEAD 13-310'' O.D. CASING

3,000 P S I W.P. 9-518" O.D. CASING

5-112'' O . D . CASING 2-310'' O.D. TUBING

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