EGYPT: SILDRIL Gives Top Performance in Nile Delta Well

Transcription

1 PERFORMANCE REPORT EGYPT: SILDRIL Gives Top Performance in Nile Delta Well The operator (PETROBEL) was faced with drilling a 8½ hole through reactive Kafr El-Sheikh shales and unconsolidated sands from a window that opened in the 9⅝ casing. The use of a SILDRIL KCl silicate water-base mud yielded the required inhibition and added a degree of cohesive strength to the sands that resulted in complete success. This was the first time SILDRIL had been used in Egypt but we had the confidence in the system and the M-I technology to achieve success. The ease to use and maintain the system with such amazing results, proved that we had used the system that hits the target. Hussein Khalil, Area Engineerr Well Information Location... Nile Delta, Mansoura, Egypt Spud / Completion... April, 22 Intervals Drilled...8½ hole from 22 Meter to total of 2,81 Meter (79 Meter) Deviation... 6 The Situation After drilling of 12.2 hole to the casing 2,8 Meter using KCl/Glycol mud, and while the last conditioning trip prior running the 9⅝ casing, the hole was packed-off. A fish was left in hole. Petrobel decided to run 9⅝ casing to save the shale section of the exposed open hole. After setting 9⅝ casing at 2,13 Meter (top of fish in hole), a window was 2,2 Meter to side track the well in order to finish the reactive shale section. The formation to be drilled was highly reactive Kafr El-Sheikh Formation shale interbedded with unconsolidated sands. The off-set wells experienced down-hole losses with mud weight 1.28 Kg/L. On the other hand, the shale won t be stabilized with mud weight not less than 1.4 Kg/l. To drill this interval successfully, would require a high degree of inhibition and optimal hole cleaning. The correct mud weight together with the proper rheology profile should be applied to avoid the expected losses within the sand bodies. The Solution M-I Overseas, Egypt Branch, offered to use the same mud existed from the previous section (KCL/Glycol) and to be switched to SILDRIL system after treating out the hardness from the mud. We ve figured the weight of 1.4 Kg/L to start with. Action The system was treated out using Soda ash, and the Sodium Silicate was mixed to 12% by volume. The shaker screens were sized down from 11 mesh to 2 mesh which was allowed after observing the cutting on the shakers.

2 The Results Fast Drilling: The interval was finished in nine days includind five days drilling, two days tripping, one day for logging and one day for running 7 liner. All Targets Met: All targets were achieved as the reactive shale section was cased off together with the first 3 meter of reactive shale of the next formation. Moreover, no losses were experienced within the low pressure sand even with using higher mud weight than what used for the off-set well. Excellent Lubricity: Because of the low angle of the well, no lubricants were used while drilling the interval. But still, the degree of lubricity which illustrated from the tripping and the directional work to kick-off the well, indicated how lubricant is the SILDRIL system. Less Solids Content: Because of the big size of the cuttings drilled, the screens were sized down from 11 mesh to 2 mesh which improved the cleaning of the system from the L.G.S. Less Mud Cost: The whole interval (79 Meter) was drilled without using a single barrel for dilution which resulted in overall reduction in mud cost. No accretion: Neither bit balling nor shale sticking on BHA were observed while tripping. The Details A window was milled in the 9⅝ casing from 2,1 Meter to 2,2 Meter with a flow rate of 378 gal/min. A rat hole was drilled from 2,2 Meter to 2,2 Meter and the hole was circulated clean at 4 gal/min. The 8½ hole was drilled with a SILDRIL mud from 2,2 Meter to 2,96 Meter with tool face orientation as necessary through Kafr El Shaikh shale formation. A short trip was made, and the drill-string was run back to bottom without any problems. The hole appeared in good shape. The drilling process of 8. hole was advanced from 2,2 Meter to 2,96 Meter where the MWD failed to read survey shots. The hole was circulated clean prior tripping out of hole from 2,96 Meter to 2,2 Meterm (9⅝ window). After pulling out of the hole to replace the MWD, the same directional assembly was run in the hole. Drilling 8½ hole was continued from 2,96 Meter to 2,1 Meter with intermittent sliding. After circulating bottoms up with 437 gal/min, a wiper trip was done to check the hole. After running in the hole to 2,1 Meter, drilling continued to liner 2,81 Meter ( Meter inside Abu Madi formation). The hole was then circulated clean many times at 441 gal/min. The string was pulled out of hole from 2,81 Meter to the window for running the 7 liner. No accretion of cuttings on the drill-pipe was observed, which means that the flow rate was enough to clean hole and transport cuttings to the surface and the hole was in good shape. The 7 liner was safely run and cemented on bottom. The Mud System While drilling with the SILDRIL System, the two shale shakers were fitted with 2 mesh layered screens to improve the removal of fine solids. LSRV rheology and fluid loss (<2ml) were easily maintained with the addition of premixed Biopolymer/Drispac SL to the active system. 12% by volume of SILDRIL was added on the rig to 1,9 bbls of old Kcl/Glycol/ polymer mud remained from previous interval to drill the shale interval of Kafr El Shaikh. The composition of the SILDRIL was as follow: Additives PPB DUO-VIS (biopolymer) 2. DRISPAC SL 4. SILDRIL. KCL (Potassium Chloride) 3. Sodium Bicarbonate & Soda Ash 3. 2 bbls of premixed (same concentration) was also mixed before drilling for maintenance during drilling and potential losses. During drilling, no biopolymer (Duo-Vis) was added to the active system because the low shear rheology values were optimum from the beginning of the interval and didn t change a lot. The API fluid loss was less than 2 ml/3 min all the time which eliminated more addition of Drispac-SL. The mud weight was maintained within 1.4 Kg/L and it was decreased while drilling because of the finer screens used. The mud weight was frequently adjusted by mixing Barite.

3 Rheology Fann Reading / Depth sec Gel Strength min Gel Strength PV YP AV N K Fluid Loss Control 6 API Fluid Loss (cc's/3 min) Depth (meters) Well-bore Stabilization With the proper mud weight used, SILDRIL is the primary wellbore stabilizer additive. KCl was used as a secondary inhibitor. In combination they synergistically provide an effective wellbore stabilization system for swelling and dispersive and the reactive shale. Optimum concentration of SILDRIL is 1-12% to ensure optimum chemical stabilization performance. KCl is maintained at 1% by weight. The SILDRIL concentration was monitored using a Hach Silicate Test Kit, ph, and the mud and filtrate alkalinities. The alkalinity values were the most sensitive response to the depletion of silicate. The following calibration table compares the various parameters for standard reference SILDRIL concentrations from 7% to 1%.

4 SILDRIL Concentration vs ph, P f, M f, and Silicate Concentration. (Hach Test). SILDRIL CONCENTRATION ph P f (ml) M f (ml) Hach Test Kit (mg/l) / (diluted) 7% % % % % % % % % Graphical Comparison of SILDRIL L Concentration vs ph, P f, & M f Alkalinity (ml.2 N H2SO4) PH ph P f M f 7% 8% 9% 1% 11% 12% 13% 14% 1% SILDRIL Concentration (% by volume)

5 P m, P f, M f, and ph versus Depth SILDRIL - Alkalinities Alkalinity P m P f M f Depth (meters) Solids Control Equipment: (SHALE SHAKERS) Prior Displacement with SILDRIL System: DERRICK SHAKER #1 SHAKER #2 HIGH PERFORMANCE FINE SCREEN SHAKER After Displacement with SILDRIL System: HP11 HP11 HP11 HP11 HP11 HP11 DERRICK SHAKER #1 SHAKER #2 HIGH PERFORMANCE FINE SCREEN SHAKER HP2 HP2 HP2 Observations and Recommendations The SILDRIL System is the recommended water base system to provide optimum wellbore stabilization for shale and limestone formations, minimum dilution rate, and minimum environmental impact. The performance of the system was demonstrated while drilling the well Batra-3 Sidetrack. HP2 HP2 HP2 The inhibition of the SILDRIL System was also demonstrated with the improved integrity of the cuttings in the Kafr El Shaikh shale. The well-site geologist commented on the improved condition of the drilled cuttings for identification. After drilling the Kafr El Shaikh shale, a wiper trip was made without any excess torque and drag. Following the wiper trip, the string was run directly to bottom without circulating or washing. The trip out of the hole to run the liner was also made without any significant problems. On the trip out of the hole, no accretion of drill cuttings was observed on the drill pipe. The use of lubricant was not deemed necessary because the torque observed with the SILDRIL System showed no appreciable difference. Questions? We ll be glad to answer them. If you would like to know more about SILDRIL and how it s performing for our other customers, please call the M-I office nearest you.

6 Attached, please find hereafter the scanned copy of: Calliper log Lithology description versus torque readings Estimated pore pressure with actual pore pressure reading took from the field versus used mud weight This information is supplied solely for informational purposes and M-I SWACO makes no guarantees or warranties, either expressed or implied, with respect to the accuracy and use of this data. All product warranties and guarantees shall be governed by the Standard Terms of Sale. Nothing in this document is legal advice or is a substitute for competent legal advice. P.O. Box Houston, Texas questions@miswaco.slb.com 212 M-I L.L.C. All rights reserved. Mark of M-I L.L.C. FPR.191a.128.R1 (E)