A novel triple action load cell assembly (LCA) was developed to determine three index parameters reflecting compressive, tensile and shear characteristics of mudcakes. The results indicate that the tensile, compressive and torsional behaviour of mudcakes are strongly influenced by the physics and chemistry of the mud additives.

Eine neuartige dreifach wirkende Druckkammer zur Bestimmung der drei Indexparameter Druck, Zug, und Scherung von Spuelungskuchen wurde entwickelt. Die Ergebnisse weisen auf einen starken Einfluss der physikalischen und chemischen Spuelungszusatze auf Druck, Zug, Scherung hin.

Un assemblage d'une nouvelle cellule a triple action (LCA) a ete developpee pour determiner trois paramètres caracterisant la compression, la contrainte en traction et la resistance à la fracture des cakes. Les resultats indiquent que les comportements tensile, compressif et de torsion des argiles sont fortement influences par la chimie et la physique des additifs des boues.


Polymers, chemicals and other mud additives influence mudcake matrix rigidity and textural quality by trapping or associating them in a three-dimensional matrix of closely packed particles with some micro/macro voids within the mudcake matrix. The molecular and electrical forces associated with polymers, chemicals and other additives control the compressive, tensile and shear characteristics of mudcakes. Since variation in the bulk matrix rigidity as well as the resistance of the interfacial materials provide a good indication of the likely mechanical characteristics of mudcakes formed by different mud systems, any index parameter related to the bulk or interfacial matrix material characteristics will be an effective means for mechanical characterisation of mudcakes.

Several investigators have pointed out the variation of mudcake properties due to the variation of physical, chemical and electrical properties of mud additives forming the cake and the nature of interactive forces prevailing during the period of deposition (Annis and Monaghan, 1962, Outmans, 1974 and Amanullah and Tan, 2000). Harden and Welch (1961) reported laboratory results showing variation of forces necessary to move a steel pipe on the filter cake with a variation in the composition of the mudcake. According to Amanullah and Tan (2000) muds producing soft and thick mudcakes increase the potential of differential sticking. Isambourg and Marti (1999) pointed out mudcake hardness as one of the parameters which governs differential pressure sticking problem. According to Warren (1940) bit and/or BHA balling may occur as a result of the accumulation of filter cake on the bit or BHA during pulling a drill string. The scope of this accumulation is higher for mudcakes with high adhesive properties. Embedded cuttings bed formation is highly influenced by the compressive characteristics of mudcake (Amanullah and Tan, 2001), ease of recovery of a stuck pipe is related to the pull resistance of mudcakes (Amanullah, 2002) and the excessive torque of drill string is closely related to the torsional resistance of mudcakes.

Preparation of Mudcakes

The formulation of the muds is given in Table 1. The mudcakes were prepared using an API filter press by running the filtration test for a period of time to produce 100 cc filtrate.

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