Field Results of Cementing Operations Using Slurries Containing a Fluid -Loss Additive for Celnent
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SQUEEZE CEMENTING Field Results of Cementing Operations Using Slurries Containing a Fluid -Loss Additive for Celnent J. P. PAVLICH DOWELL DIV. OF THE DOW CHEM/CAL CO. MEMBER A/ME HOUSTON, TEX. W. W. WAHL TULSA, OKLA. Downloaded from http://onepetro.org/jpt/article-pdf/14/05/477/2213292/spe-133-pa.pdf by guest on 26 September 2021 Abstract Casing cementing operations utilizing low-fluid-loss slurries showed an extremely high success ratio, confirm A survey of 1,000 squeeze-cementing jobs in different ing the fact that this type of cement will help minimize areas of the United States indicates that cement slurries channeling, prevent sticking of casing during cementing, having low-fluid-loss properties can be used successfully increase the probability of desired fill-up and reduce the in conventional squeeze operations employing the "hesi necessity for block squeezing. tation" technique. It has been found that high pressures are not essential to obtaining a successful dry test follow The application of cement slurries during oil well ce ing squeeze. Also, zone isolation to reduce high gas-oil menting operations is frequently complicated by excessive or water-oil ratios has been achieved by notching the water loss into permeable formations. This results in pre casing with high-velocity jets of an abrasive-laden fluid mature thickening of the slurry and possible bridging of and subsequent displacement of low-fluid-loss cement at cement solids before placement of the slurry is complete. high injection rates. The attainment of high squeeze pressures is frequently misleading in that they may be due to blockage by Bridging agents in gel-cements containing the fluid-loss additive have been used to squeeze naturally fractured dehydrated slurry in a region of fluid-loss, rather than in the zone to be sealed off. The inclusion of fluid-loss addi formations which previously required numerous stages tives in cement slurries reduces premature fluid-loss and with large volumes of cement. Drilling-out was not re minimizes the possibility of improper placement of the quired in many cases, because the cement was circulated cement and subsequent job failure. out of the perforated interval. Casing cementing opera tions have been particularly successful when using light In the past, many fluid-loss control additives have re weight slurries containing pozzolanic extender, bentonite sulted in undesirable modification of many slurry proper and sufficient fluid-loss additive to reduce the fluid-loss ties, complicating application procedures and often requir to 120 eel 30 minutes at the cementing temperature. ing the use of additional corrective additives. A recently Cement bond logs indicate that these slurries, when used developed fluid-loss additive, FLAC, is relatively inert with scratchers and reciprocation of the pipe during the and in most cases does not affect the desirable properties cementing operation, increase the probability of desired of either the cement slurry or the set cement.' The sum /ill-up and minimize the necessity for block-squeezing. mary chart shown in Table 1 is a breakdown of over 1,000 cementing jobs using this fluid-loss-control additive Introduction which have been performed in the major oil fields of the U. S. and Canada. These treatments are divided into the A study of treatment reports from over 1,000 cement following broad categories. ing jobs, using slurries with controlled fluid-loss properties, 1. Zone Abandonment-shutting-off perforations to ex indicates that in most applications controlled filtration clude undesirable fluids and to permit reworking of well. provides ,definite advantages in achieving the purpose of the cementing operation. Analysis of the economic aspects lReferences given at end of paper. of squeeze cementing indicates that the use of a low-fluid TABLE I-CEMENTING JOBS PERFORMED USING LOW-FLUID-LOSS loss additive in the slurry provides at least 10 per cent CEMENT SLURRI ES lower cost over conventional squeeze-cementing operations Zone General Block Zone IPrimary employing neat cement by eliminating extra stages. Un Area ~andonmen! Repair Squeeze L~!ati~~ ~mpleti?~~ Misc!. successful squeeze jobs were studied from the standpoint Gulf Coas~ 289 65 57 2 24 73 Permian Basin 165 63 of formation characteristics, cementing materials and tech Kansas-Okla.- Texas Panhandle 64 40 .5 niques in an effort to determine causes of failure and Rocky Mountain possible remedies. and 4-Corners 45 ~O Ark-La·Tex 20 10 15 Appalachian 45 18 Original manuscript received in Society of Petrolewn Engineers office Canada 45 20 Sept. 7, 1961. Revised manuscript received April 10, 1962. Paper pre Per Cent of ' sented at 36th Annual Fall Meeting ef SPE, Oct. 8-11, 1961, in Dallas. Jobs Succesc;ful 80 VO 72 60 100 70 MAY, 1962 SPE 133 477 2. General Repair-squeezing-off channels and repair in the cement slurry is more than offset by eliminating ing holes in pipe. the expense of additional squeeze stages that might other 3. Block Squeeze-isolating a zone before perforating wise be necessary to obtain a dry test. Additional savings for production. are effected by omitting the drilling-out step normally 4. Zone Isolation-Squeezing to eliminate vertical mi required after squeezing with conventional high-water-loss gration of fluids or gases (often referred to as "pancake" slurries. squeeze) . The success ratio of cementing jobs using low-fluid-loss 5. Primary Completion-setting casing or liners. slurries has been relatively high. In areas where formations are highly permeable, fractured or vuggy, and perfora 6. Miscellaneous-tubingless and permanent-type well tions cover an extended interval, these techniques have completions. proved 85 per cent successful. A successful job is defined as one in which a dry test was obtained following a single-stage application. Zone Abandonment Some of the early low-fluid-loss jobs were unsuccessful Conventional squeeze techniques designed to seal off a because of improper squeeze techniques. Multiple stages specific zone or set of perforations rely upon spotting were necessary because field personnel were unable to the cement slurry at the desired depth and then dehy accept the idea that a satisfactory shut-off could be drating it by the application of high pressure, forcing obtained without using high squeeze pressures. Many excess liquid from the slurry out into the formation. If, times, an adequate squeeze pressure was obtained, indi Downloaded from http://onepetro.org/jpt/article-pdf/14/05/477/2213292/spe-133-pa.pdf by guest on 26 September 2021 after placement, the well does not give a "dry test", addi cating that cement filter-cake build-up had progressed tional stages of cement must be applied until a successful satisfactorily. However, in an attempt to attain still higher seal is obtained. squeeze pressures, the formation was hydraulically frac tured and once more opened up. Additional slurry was Many things can contribute to job failure during a only pumped away into the formation, rather than being squeeze-cementing operation. A frequent cause of failure dehydrated to form a permanent seal at the wellbore, is premature dehydration resulting from rapid fluid-loss and the job was considered a failure. Obviously, the ideal and subsequent immobilization of the slurry.' Sometimes, procedure is a slow pressure build-up which will gradually when a long perforated interval is to be shut off, dehydra force the excess water from the slurry without pushing tion occurs rapidly when the first perforations are con the slurry away from the wellbore, possibly resulting in tacted, and the resulting cement filter-cake that builds up formation damage. blocks the slurry from reaching the remainder of the Normally, it was found that pressures ranging from perforations. As a result, even if only a few of the 500 to 1,000 psi in excess of the bottom-hole injection perforations remain open, fluid can enter the well bore and pressure were sufficient to attain a successful squeeze. the job must be considered a failure. The value of a The bottom-hole injection pressure is that pressure at fluid-loss additive to prevent premature water loss before tained once injection has become stabilized. The surface the slurry can be properly placed and squeeze pressures squeeze pressure can be calculated from the bottom-hole applied is readHy apparent. squeeze pressure and the hydrostatic head of the fluid The use of "hesitation" squeeze techniques has been column in the well. found beneficial in attaining an effective seal by the Table 2 illustrates that low final squeeze pressures can gradual building-up of a cement filter cake. Essentially, this consists of applying successively higher pressures at intervals, with pauses between, to allow controlled deposi TABLE 2-EfFECT OF SQUEEZE PRESSURE ON JOB SUCCESS tion of cement solids. This procedure is not recommended Squeeze Pressure In Excess of Bottom-Hole for use with high water-loss slurries because there is ,Well i.njection Pressure Depth danger of dehydrating the entire column of slurry. With County State ----'!tL Attempted lAttained -Remorks* controlled water-loss slurries, however, the desired cement Chambers Tex. 11,000 2000 i200 PC R filter cake can be slowly built up in the perforations until Qnd Stage ;1000 1000 PC they are completely sealed, while the slurry in the hole R 3rd Stage 1000 1000 DT remains fluid and may be reversed out when squeeze Chambers Tex. 9,500 ·1000 1000 DT Chambers Tex. 5,000 2000 850 DT pressures indicate that an effective shut-off has been Jeff. Davis Miss. 14,565 2700 2700 DT attained. Jeff. Davis Miss. 12,800 750 750 DT Simpson Miss. 13,750 2800 800 PC R As cement fills a perforation, the filter cake continues 2nd Stage 800 800 DT to grow, forming a protrusion into the interior of the Jeff.