Sustainability in Re-cycling Drilling Fluids Between Rigs

Abstract

Abstract ADCO is drilling a highly deviated holes through long section of unstable shale formations which require a drilling fluid system to inhibit such shale and stabilize the wellbore as experienced hole problems such as sloughing, hole packed off and hole collapsed. This will result in rig lost time due to stuck pipe, plugging back and sidetrack. Water Base Mud system was used to drill such deviated section but due to swelling and hydration of the shale within short period resulted in hole collapsing and excessive non productive time. The directional drilling through the shale could reach to 70 degree at the bottom of the shale formation with high build up rate. The hole cleaning is critical and requires drilling technology such as sing Rotary Steerable system and drilling practices to ensure good hole cleaning. Oil Base mud are expensive but are worth the cost when drilling through troublesome shales that would otherwise swell and disperse in water base mud. Thus, ADCO is drill these shally sections using the oil base mud on large scale across all ADCO fields successfully due to wellbore stability and resulted in running & cementing liners at bottom without any problems. Once the drilling operations completed, the solids content must be minimized and the mud has to be run through the centrifuge for de-bariting. Thereafter can be loaded into haulage trucks whereby sent to mud plant for treatment and stored in storage tanks for re-use. The oil base mud (1500-2000 bbls) should be transferred to mud plant for treatment. Accordingly, a re-cyclying and re-conditioning mud plant was built to be used for the storage and treatment of oil base mud and brine services respectively require to be used for drilling and rigless operations. In addition, the formation pressures of wells are high which require heavy brine to be used in order to have sufficient hydrostatic head to control the well. Non damaging fluid is used to drll all reservoirs which is mainly consists of brine (CaCl2, CaBr2 or NaBR) with the addition of viscosifiers and water loss reducers. After completing the deviated section then the non damaging fluid is centrifuged to get rid off the solids and transferred to other rigs for use otherwise will be sent to mud plant for storage and reuse. Moreover, the inhibited filtered brine is prepared to be used as completion fluid and to be left in the hole as packer fliuid. The excess of fluid has to be collocted and transported by dedicated haulage tankers to othe rigs for re-use. Moreover, ADCO rigless operation requirement is to use brine of different mud weight which varies from 75 pcf up to 106 pcf based on the formation pressures. We are preparing in the plant the required brine and send to these rigless operations for killing purposes to secure the wells and also for production testing packages for displacing the fluid inside the production testing string.