SPECIAL TECHNIQUES AND EQUIPMENT REDUCE PROBLEMS

Robert A. Joseph
OXY U.S.A. Inc.
Houston

Novel underbalanced drilling procedures, downhole-adjustable equipment, and a mud easily cleaned from the fractures, helped reduce formation damage and ensured a successful horizontal well in the high-temperature, abnormally pressured Austin chalk in Louisiana.

The technique for successfully drilling the lateral in the Austin chalk included taking the smallest influx possible, maintaining as low a back pressure as possible, and balancing the mud gains from the hole with the mud losses to the hole. Other keys to the success of this well included the use of measurement-while-drilling (MWD) with resistivity in real time to pick the top of the formation.

The mud formulation was critical because of the high bottom hole temperature and saltwater and CO2 contamination. The mud required a low gel strength so it would flow back from the fractures for better cleanup. Offset wells had production problems possibly related to formation damage from the drilling fluids.

The Monroe A No. 1 was spudded on Dec. 14, 1993, and drilling proceeded according to plan from surface to 13,950 ft. The goal of drilling a very straight vertical hole was achieved. The arithmetic average of all the multishot survey points from the surface to 13,950 ft was only 0.83; the maximum inclination was 1.8 at 7,502 ft.

At 13,950 ft, the 12 1/4-in. curve building assembly was picked up (Table 1)(17454 bytes). The assembly included a 12 1/4-in. milled tooth bit, 8-in. adjustable bent-housing mud motor set at 2.2, and a directional/gamma ray/resistivity measurement-while-drilling (MWD) probe.

The assembly was designed to build angle at a rate of 10/100 ft.

Drilling progressed to 14,376 ft, building angle to 34.7 at a rate of 8.2/100 ft. After the well reached 14,455 ft, the hole packed off during reaming at 14,370 ft, and the hole below 14,365 ft had to be redrilled. The 12 1/4-in. hole was drilled to 14,531 ft measured depth (MD), or 14,478 ft true vertical depth (TVD), and reached an angle of 39. The mud weight at 14,531 ft was 10.7 ppg.

Based on formation samples and the MWD resistivity log correlation, the well penetrated 22 ft TVD into the Austin chalk. Because of concerns about drilling too deep and encountering a high-pressure fracture, the drilling assembly was pulled, and wire line logs were run. The top of the Austin chalk was picked at 14,448 ft TVD.

After the logs were reviewed, an additional 57 ft were drilled to 14,588 ft MD (14,514 ft TVD) to ensure the casing would be set in a more competent chalk section, correlative to the casing point used by Sonat Exploration in the Brookeland field.

That action addressed another concern, that the marl section at the top of the chalk might not provide a strong enough shoe.

INTERMEDIATE CASING POINT

The 9 5/8-in. casing was run to 14,585 ft and cemented with 2,900 sacks of cement with no problems. A temperature survey located the top of cement at 7,300 ft.

After the casing head was installed, the 32.3-ft tall, 11-in., 10,000-psi blowout preventer (BOP) and snubbing stack were installed. The annular preventer was placed in the middle of the stack between two sets of stripper rams to serve as a portion of snubbing riser, thereby minimizing the overall height of the stack (Figs. 1 (92085 bytes)and 2 (80318 bytes)).

For drilling and stripping operations, the entire stack was contained below the rig floor with the rotating head as the top component. For snubbing operations, the rotating head was removed and replaced with an 11-in. riser and an additional set of stripping rams placed above the rig floor.

Camlock crossover flanges were installed between the rotating head and the ram preventer immediately below it. This setup allowed the rotating head to be rigged down quickly and pulled through the 37 1/2-in. rotary and the snubbing riser to be run back through the rotary and connected to the stack quickly.

A 3-in.-bore remote hydraulic choke was added to the choke manifold as the primary drilling choke. The existing 2-in.-bore remote hydraulic choke was retained as a backup. Dual gas busters, flare lines, and skimmer tanks were installed downwind of the mud tanks. The BOPs were tested to 250 psi and 10,000 psi; the 9 5/8-in. casing was tested to 7,400 psi.

The casing shoe was squeezed once to obtain an 18.5-ppg shoe test. Because of the high injection pressure and low injection rates, a cement retainer was used for the squeeze.

PILOT HOLE

The 10.8-ppg mud was displaced with a new 13.5-ppg dispersed polymer water-based mud. A completely new mud system was built to avoid exposing the objective zone to the drilled solids, asphalts, lost circulation material, and excess clays present in the old mud. An added benefit was that the new mud with its low clay content was able to withstand several severe CO2 influxes from the chalk without developing an unmanageable viscosity problem.

The original plan was to drill the pilot hole with a polycrystalline diamond compact (PDC) bit, but this plan was changed when it appeared there was still metal debris in the hole after the retainer had been drilled up. Therefore, an 8 1/2-in. milled-tooth motor bit was run on a 1.2-bent-housing mud motor and directional MWD/gamma ray tool. Angle was built to 46 to facilitate the lateral kick-off and was then held at 46 as the bit drilled ahead on tangent and as mud weight was increased to 14.1 ppg.

Mud weight was intentionally kept low to ensure that a kick would be taken when the first fracture was encountered. The shut-in drill pipe pressure from the kick would be used to determine the zone's pressure. If the fracture were penetrated with a high mud weight, circulation would probably be lost before a bottom hole pressure could be determined.

If the pilot hole encountered a fracture, the plan was to try to drill slightly overbalanced to determine if overbalanced drilling were feasible. Because the pilot hole was to be plugged off, and mud loss in the pilot hole was not a concern, the snubbing equipment was not used for the pilot hole.

At 14,831 ft MD (14,688 ft TVD) the well kicked and was shut-in with 1,030 psi on the drill pipe, equivalent to 15.5 ppg. The well was killed with 16.2-ppg mud, and overbalanced drilling continued to 14,848 ft MD (14,700 ft TVD), at which point the well began to flow.

Underbalanced drilling was begun with 150-200 psi of back pressure. A third kick occurred at 14,893 ft MD (14,731 ft TVD). Shut-in casing pressure increased to 2,880 psi. The mud weight was increased to 16.7 ppg and underbalanced drilling resumed. At 14,975 ft, the bit had to be pulled.

An attempt was made to kill the well with 17.4-ppg mud, but the hole began taking fluid. The drillstring was stripped out of the hole under 190-psi casing pressure, and an amount of mud equal to pipe displacement and capacity was pumped down the annulus as the pipe was pulled. By the time the bit reached the surface, the well was dead. A new bit was run in the bole, and mud weight was cut to 17.0 ppg in stages to establish full circulation.

The pilot hole was drilled to a total depth of 15,150 ft MD (14,909 ft TVD). The MWD tools recorded a gamma ray log of the pilot hole for later correlation during drilling of the lateral. A 250-bbl, 17.6-ppg pill was spotted at the casing shoe prior to pulling out of the hole to run wire line logs. By the time the wire line lubricator could be installed, casing pressure had reached 90 psi.

The logging tools reached a maximum depth of 14,876 ft. An MWD tool was run in the hole on the drillstring to obtain resistivity, gamma ray, and density/neutron logs, instead of trying to condition the hole for another attempt to log under pressure with wire line tools. The base of the chalk was picked at 14,805 ft TVD in the pilot hole.

Because the top of the chalk was encountered deeper and the casing was set deeper than originally planned, the kick-off point (KOP) for the lateral was made immediately below the 9 5/8-in. casing shoe. Because a fracture identification log was not run, the depth for the lateral was based on the shows in the pilot hole and the interval that had been completed and tested in the Gulf well. The best-looking interval in the Monroe pilot hole was at 14,674-14,743 ft TVD; the interval tested in the offset Gulf Wilson & Johnson No. 1 well was 14,683-14,796 ft.

Thus, the lateral would start at a depth of 14,710 ft TVD and aim for a depth of 14,787 ft TVD (Fig. 3 (107555 bytes)). This course would make the lateral traverse the heart of the chalk section that was tested in the Gulf well and was believed to contain the greatest concentration of fractures.

The average angle of the lateral would be 88.94. There would be no high-side tolerance and a 15-ft low-side tolerance at the start of the lateral, and a 15-ft high-side tolerance and 5-ft low-side tolerance at the end of the lateral.

8 1/2-IN. CURVE

Although an open hole sidetrack was possible, the pilot hole was plugged off to eliminate the complication of having another source of flow open to the well while the lateral was drilled. Because the well would not remain static, the potential for setting a successful balanced cement plug was very small. Therefore, a cement retainer was set on wire line at 14,525 ft, and a cement plug was squeezed below the casing shoe.

After the retainer was drilled out and the plug dressed off, a milled-tooth motor bit, 2.5-bent-housing mud motor, and directional MWD with gamma ray were picked up to kick off the lateral (Table 2 (19476 bytes)). The design build rate was 13.05/100 ft.

The well was sidetracked by time-drilling on the low side of the hole at 14,595 ft. After the bit was dulled and pulled, a Hughes R-447L PDC bit was used to build angle to 77 at a rate of 14.7/100 ft.

At 14,866 ft with a 16.8-ppg mud, the first fracture in the lateral was encountered, and underbalanced drilling was begun. At 14,913 ft with 16.7-ppg mud in the hole, the bottom hole assembly (BHA) was tripped to change the motor to a 1.2 bent-housing and change to a Hughes R-382GN PDC bit.

SNUBBING

The trip from 14,913 ft became the first and only test of the snubbing/stripping technique. The well was dead during the trip out, but it began to flow while the BHA was picked up. The stripping rams were used to run the pipe back in the hole under 1,400 psi. By the time the trip was completed, the casing pressure had risen to 2,880 psi, and the hole took 75 bbl of mud as drilling resumed. The trip in the hole took 1 1/2 days and required the stripping ram elements to be changed out twice.

From this trip, it appeared that the snubbing technique would be no more effective at minimizing the amount of mud lost to the hole on trips than spotting high-weight pills and using volumetric control. Also, this method was longer, more complicated and difficult to coordinate, and more expensive. Thus, the snubbing equipment was not used again during the remainder of the well program.

LATERAL

The curve was landed at 88.6 at 15,198 ft MD (14,723 ft TVD). Drilling proceeded in the lateral with a 16.7-ppg mud and 200-800 psi back pressure. From 15,434 to 15,454 ft, the bit slowed to less than 2 ft/hr in the slide mode. The mud weight was increased to 17.1 ppg, and the bit was pulled.

The bit had 37 missing or damaged cutters, mostly on the bit face. The damage was believed to have been caused by a pyrite streak. The bit was replaced with a new R-382GN, the mud motor was replaced with a 1.0 high-speed motor, and a downhole-adjustable stabilizer was run immediately above the motor to facilitate increasing or decreasing angle in the rotary mode (Table 3 (18329 bytes)).

When sufficient hole had been drilled to allow surveying the hole drilled by the damaged bit, the hole was found to have dropped from 89 to 86.3 in just 62 ft. The hole was projected to be at 14,734 ft TVD, which was 15 ft below the target line. The suspected cause of this sudden drop was that the damaged bit acted like a sidetrack bit. Aided by gravity, with most of its face cutters gone and its side cutters still intact, the bit had tremendous side cutting action, causing the hole to drop angle quickly.

To return to the target line, the hole would have to drop another 3 ft to 14,737 ft TVD before 90 could be achieved, and an additional 300 ft of lateral would be drilled below the target line. Because a large saltwater influx was already occurring, the bit was pulled back to 15,000 ft to drill an open hole sidetrack rather than to cut lower into the chalk and increase the risk of encountering even more saltwater. By this time the mud's chlorides level had climbed from 800 to 5,000 ppm, and the mud had a 5% oil content. In addition, considerable CO2 was encountered, causing difficulty in maintaining mud properties.

The new lateral was kicked off at an 84 angle at 15,000 ft MD by time-drilling on the low side of the hole. A 90 angle was achieved at 15,165 ft MD (14,720 ft TVD). At 15,870 ft, a slide was made to drop the angle below 89. Unfortunately, once the drop tendency was started, it could not be stopped. At 16,228 ft, the BHA was pulled because angle had dropped to 86.6. All BHA components were found to be in order, so the motor was changed from the 1.0 long-housing, high-speed motor to a 1.3 short-housing, low-speed motor to improve the build tendency. The change worked; angle was brought back up to keep the well on target.

To a depth of 16,500 ft, only moderate drag occurred during pulling out of the lateral. All trips from beyond 16,500 ft, however, required a considerable amount of backreaming from the bit depth back to 16,500 ft to pull out of the lateral. At 16,803 ft, after the third MWD failure in the lateral, the collar-mounted directional/gamma ray tool was laid down, and a wireline-retrievable MWD probe was picked up. The wireline-retrievable tool was a directional tool only, which eliminated the real-time gamma ray log for the remainder of the horizontal section.

The trip to surface from 16,803 ft was the last until the total depth of 19,100 ft was reached.

Primarily because of the high temperatures, there were four more MWD failures after 16,803 ft. Because the MWD probe was wire line retrievable, the bit was pulled only back into the casing to retrieve the probe. The standard procedure was to pull the bit back to 13,950 ft into the vertical part of the hole, retrieve the tool with a wire line overshot, and pump down a new tool. The bit was tripped back to bottom, staging mud out of the lateral both to cool the tool and to reduce the potential for losing circulation.

Eliminating the need for a round trip from 13,950 ft to replace the MWD played a major role in the success of this drilling operation. The time to replace a tool was reduced from 3 days to 1 1/2 days. Furthermore, the ability to return the bit to bottom much sooner meant that the mud left in the lateral during the trip had considerably less degradation from high-temperature gelation and CO2 and saltwater contamination. This reduced exposure time improved the ability to circulate this mud out of the hole without losing returns.

By the time 18,403 ft was reached, the static bottom hole temperature had increased to 311 F. Circulating temperatures had increased from 213 to 295 F. since the start of the lateral, and the MWD was now failing after just a few hours on bottom. Because of the temperature-induced MWD failures, the lateral was drilled "blind" from 18,241 to 19,100 ft.

Short trips back to the casing were made at 18,403 ft and 18,834 ft to replace the MWD probe. In each case the MWD lasted long enough to survey the footage that had just been drilled blind, but it failed before any newly drilled hole could be surveyed. During this blind drilling, the hole dropped angle from 89.3 at 18,397 ft to 85.7 at 18,802 ft. The hole was drilled blind from 18,802 ft to a total depth of 19,100 ft with the adjustable stabilizer in the retracted position to build angle.

The total depth of 19,100 ft MD (14,803 ft TVD) was reached on Apr. 24,199-4,132 days after spud. Figs. 4 (142882 bytes)and 5 (51360 bytes) show the well summary and directional summary for the lateral.

Four round trips to the surface were made while the lateral was drilled: at 15,454 ft (original lateral) for an MWD failure and damaged bit, at 15,643 ft for an MWD failure, at 16,228 ft for a BHA change, and at 16,803 ft for an MWD failure. After 16,803 ft, three short trips were made into the casing to change out the wireline-retrievable MWD probe. These trips were made from 17,500 ft, 18,403 ft, and 18,834 ft.

BIT PERFORMANCE

One Hughes R-382GN bit with 3/8-in. PDC cutters drilled from 15,000 to 16,803 ft, averaging 8.63 ft/hr, on both high-speed and low-speed mud motors. At 16,803 ft, a more aggressive Hughes R-482GN with 1/2-in. cutters was run on a low-speed motor. This bit drilled the remainder of the hole from 16,803 to 19,100 ft and averaged 15.96 ft/hr.

The high-speed motors averaged 370 rpm, and the low-speed motors averaged 200 rpm.

UNDERBALANCED DRILLING

The pilot hole proved that it was not possible to drill the Austin chalk overbalanced while maintaining circulation.

Therefore, the technique used for drilling the lateral was to take the smallest amount of influx possible, and maintain as low a back pressure as possible, while balancing the mud gains from the hole with the mud losses to the hole.

A back pressure of 200-800 psi was held while the lateral was drilled. As a gas bubble would near the surface, the casing pressure would increase above 800 psi. Drilling would have to be stopped until the bubble was circulated out and the casing pressure reduced.

Casing pressures reached as high as 5,040 psi during bottoms-up circulation after trips.

MUD PROPERTIES

From 15,000 to 16,200 ft, the mud weight was 16.7 ppg. As the lateral progressed, lower mud weights had to be used to maintain circulation and lessen the amount of mud lost to the hole. At 16,573 ft, the hole began taking 16.6-ppg mud at a rate of 2 bbl/min. After the mud weight was cut to 16.5 ppg, full returns were re-established. By 19,100 ft, the mud weight had been reduced to 16.3 ppg to maintain full returns during drilling.

Trips out of the hole were made by stripping back into the casing under pressure, increasing mud weight to 17 ppg, stripping out of the hole against the rotating head, and filling the annulus with a quantity of mud equivalent to the volume of steel and mud removed. On most trips, as pipe was pulled out of the hole and replaced by slightly heavier mud, casing pressure steadily decreased such that the hole was dead by the time the bit reached the surface.

Beyond 16,803 ft, there was difficulty regaining circulation after trips. On tripping in the hole, the heavy mud used for the trip was circulated out in stages. Several times the mud on bottom was so viscous that an unweighted, viscous water pill had to be spotted in the annulus to lower hydrostatic pressure sufficiently to lift this thick mud and restore full circulation. During the trip from 18,834 ft, circulation was lost twice but was regained by pumping viscous water pills and inducing a kick.

The total chlorides and oil percentage in the mud fluctuated as the lateral was drilled. Their concentrations increased as influxes were taken and decreased as additional mud volume was built and added to the system every day. The chlorides and oil in the mud increased as the lateral was drilled farther out and reached maximum values near the end of the lateral.

The maximum mud chloride reading was 15,000 ppm; the Austin chalk formation water chlorides were 25,000 ppm. The maximum oil concentration in the mud was 18%. Because the Austin chalk's oil staved emulsified in the mud, no attempt was made to skim oil from the mud. Laboratory tests showed that the mud could tolerate oil concentrations as great as 30% before the barite would become oil wet.

The hole took an estimated 2,863 bbl of mud during 39 days of underbalanced drilling operations. An additional 2,012 bbl of mud were lost to the hole during completion operations. During underbalanced drilling operations, the circulating system was extremely dynamic. it was not uncommon to change from a position of having lost 150 bbl of mud to the hole to gaining back that volume plus an additional 150 bbl over the span of a couple of hours.

The mud company took samples of mud from the well each week for lab analysis and heat-aging tests. Static shear was the property believed to best represent the ability of the mud to flow back from a fracture.

The prespud lab tests showed that the mud had a static shear 500 lb/100 sq ft after 22 days at 300 F. A value this high led to pessimism about the mud's ability to flow back from the chalk's fractures after drilling was completed.

At the start of the lateral the static shear of the field mud measured 700 lb/100 sq ft. Starting with a sample taken during drilling at 15,232 ft, however, the static shear dropped considerably to 30-70 lb/100 sq ft.

The mud company's explanation for the decrease follows: The CO2 contamination in the early portion of the lateral caused the initial static shear strength of the mud to surpass the values in the prespud lab tests. Once the CO2 had been treated and kept under control, the system underwent several other modifications that caused the static shear strength to decrease. The large amount of saltwater influxes increased the chloride content of the mud, which inhibited the ability of the bentonite and clays in the mud to yield. In addition, fresh mud containing less bentonite was continuously being added to the system to make up for downhole losses. The methylene blue test (MBT) for the system dropped from 10 lb/bbl to 6 lb /bbl.

The combined effect of these influences was to create the mud that was not successfully formulated in the lab prior to spud. This mud performed well as a stable drilling fluid, transporting cuttings from a horizontal hole and tolerating 300 F. temperatures and saltwater and CO2 contamination, while maintaining a low gel strength for an extended time for later flow back from a fracture.

HIGH TEMPERATURE

Because high bottom hole temperatures and the resulting downhole tool failures were expected to be a major problem, all aspects of this drilling operation were examined for ways to reduce the circulating temperature.

Although the skimmer tanks' normal function is to separate oil and water, their main purposes on the Monroe A No. 1 project were to provide a place for safe, efficient degassing of the mud and to increase the surface retention time for the drilling mud to reduce its temperature.

Annular disposal of the reserve pit fluids down the 13 3/8-in. x 9 4/8-in. annulus began shortly after the lateral was started. It was hoped the injected fluids would cool the annulus and help reduce downhole temperatures. Comparative data indicated that there was no significant reduction in downhole temperatures from annular injection, however.

DIRECTIONAL DRILLING

Largely because of the adjustable stabilizer (Fig. 6 (79657 bytes)), 95.6% of the lateral footage was drilled in rotary mode, and only 4.4% was drilled in oriented mode. Inclination was maintained between 85.7 and 90.7 overall and between 86.4 and 90.7 when the MWD was operational.

The adjustable stabilizer was invaluable to the success of the well, because the tool reduced the amount of slide drilling required. Sliding became progressively more difficult as the lateral was drilled. After 2,000 ft of lateral had been drilled, sliding became so difficult that a glass-beads-and-lubricant spot was required to initiate a short slide. The last slide made in this hole was 17,10617,112 ft.

The adjustable stabilizer was set and locked, by set down weight and pump operation, in either an 8 1/4-in. extended or 7 3/4-in. retracted position. In the retracted position, the stabilizer promoted building angle in rotary mode. Extended, the stabilizer promoted maintaining or dropping angle in rotary mode.

In the lateral there were seven MWD failures, most from high temperature, but there were no mud motor failures. The last motor used, a 6 3/4-in. Nortrak Mach 1, ran for 144 drilling hr and 83 1/2 circulating hr. Remarkably, the motor was downhole for 15 consecutive days and did not fail.

COMPLETION

At total depth, a pumpdown gamma ray tool was run, and the hole was logged through drill pipe from 18,860 to 14,300 ft. The BHA was backreamed out of the hole to 16,938 ft and pulled to 14,600 ft. At 14,600 ft, the mud weight was raised from 16.6 to 17.1 ppg. The drilling assembly was pulled out of the hole to run a 5 1/2-in. preperforated liner.

After the assembly was pulled out of the hole under static conditions and casing tools were rigged up, the well began to flow, so the bit was run back to 11,400 ft. Circulation could not be established. The bit was pulled to 10,465 ft, and the mud weight was increased to 17.4 ppg. The bit was pulled, and this time the well remained static.

The 5 1/2-in. liner was run on a 9 5/8-in. x 7-in. Lindsey type HSSB hydraulic-set liner hanger that allowed the liner to be rotated as it was run in the hole. The liner also was designed to accommodate an optional 2 3/8-in. internal tubing string to provide the ability to wash down the liner.

There were no problems running the BHA and 5-in. drill pipe to bottom, but there was concern that the well might kick while the liner washdown string was picked up, the liner was run without the washdown string. The liner measured 5,167 ft and included 4,425 ft of pipe with four 1/2-in. holes per foot at 90 phasing.

When the liner shoe reached 9,260 ft, the hole stopped giving returns. With the hole standing full but not giving returns, the liner was run to 17,052 ft, requiring some reciprocation to work through several tight spots. Below 17,052 ft, the liner had to be rotated and reciprocated to work it into the hole. At 18,536 ft, the liner stopped and could not be worked deeper. This depth coincided with the depth at which the hole began dropping angle at a rate of 1.3/100 ft while drilling blind. The liner hanger was set, placing the liner from 18,536 to 13,371 ft.

After a polishing mill and casing scraper were run, a multifinger caliper survey was run in the 9 5/8-in. casing. The casing was in excellent condition with the greatest wear being a 14% wall thickness reduction at 3,900-4,000 ft.

The next step was to run a liner top packer; however, the well tried to flow again. After 280 bbl of 17.2-ppg mud were bullheaded, a conditioning trip was made to 11,900 ft, and 235 bbl of 19.3-ppg mud were bullheaded; the well was finally dead, and the hydraulic-set liner top packer was run and set. A 9 5/8-in. permanent packer with seal-bore extension and pump-out plug was set on wire line at 13,341 ft. The mud was displaced with 11.6-ppg CaCl2 water, and the well was completed with a 2 7/8-in., 6.5-lb/ft, P-110 CSCB plastic-coated tubing string and a 2 9/16-in., 10,000-psi full stainless steel tree. Fig. 7 (75724 bytes) shows the completion well schematic.

The well was unloaded and flowed for cleanup, producing at about 12.9 MMcfd of gas, 3,000 b/d of condensate, and 7,000 bw/d on a 32/64-in. choke and 4,124 psi flowing tubing pressure. The maximum shut-in tubing pressure was 9,358 psi after 38 hr.

This rate was substantially greater than the best reported rate from the previously drilled central Louisiana horizontal Austin chalk wells. The encouraging performance of the well during the initial cleanup indicates the project was a success, as the well exhibited excellent inflow performance and did not appear to suffer any substantial formation damage.

The success of the project was the result of thorough prejob planning, good contingency planning, good communication and flexibility, strong contractor support, and excellent well site supervision.

RECOMMENDATIONS

Based on experiences with the Monroe A No. 1 well, the following recommendations are offered for similar wells:

Use a mud motor and PDC bit for straight hole drilling from the top of the Midway shale to the kick-off point.
Run MWD with resistivity to log while drilling and pick the top of the chalk for the protection casing point; do not run wire line logs.
Use these mud formulations; continue the practice of building a new, clean mud system after protection casing is set.
Log the pilot hole during drilling using MWD with resistivity, density/neutron, and gamma ray tools; do not run wire line logs.
Snubbing equipment is not required; make trips by circulating mud of slightly greater density.
Use atop drive.
Drill an open hole sidetrack from the pilot hole for the lateral rather than kicking off from a plug.
Use an aggressive PDC bit with 1/2-in. cutters for lateral drilling in the chalk.
Continue to run an adjustable stabilizer above the motor in the lateral section.
If drilling blind (with nonfunctional MWD), do not assume the hole follows the same inclination as the previously drilled hole, regardless of how consistent it seemed; make some allowance for the contrary tendency.
Spot heavier mud prior to picking up the slotted liner, and run the internal washdown string.