Research and Application of High Temperature and Ultrahigh Density Drilling Fluid in Deep Wells

Abstract

Drilling fluid with the high density has been successfully used in many kinds of special formations such as gypsum salt bed, salt aquifer, or compound salt formation. Some problems with this kind of the fluid, however, still have to be considered, for example the high temperature resistance in some complicated deep wells, rheological properties control, and the influence of solid content to rheological properties. The authors introduce, based on the research about some important elements such as rheological properties and the quality of sedimentation stability, a drilling fluid with the high density of 2.45 g/cm 3 that has good rheological properties, excellent qualities of sedimentation stability, low water loss, well antisloughing, and small lubrication coefficient, and which can be perfectly used in the deep slim-hole well with the high pressure salt aquifer. In addition, this drilling fluid system with the density of 2.45 g/cm 3 , no matter in the laboratory test or in the field case (No. 3 well of Jeddah), both performs excellently and controls well the salt crystallization, reducing the rate of the crystallization and preventing sticking, jets blocking, or torque increasing. Finally, with the successful application, this drilling fluid can be regarded as a good example for other deep wells or ultradeep wells with the complicated formation in Fergana Valley, Uzbekistan.

Nano-Grafted Acrylamide Copolymer as an Anti-Temperature and Anti-Calcium Fluid Loss Agent for Water-Based Drilling Fluids

“…This is because excessive water loss in the drilling fluid can quickly lead to the formation of thick filter cakes, which disrupt good drilling by causing instability in the well wall. As high temperatures can affect drilling fluid rheology and make it difficult to keep the filter volume within a safe range, they pose a significant threat to the temperature resistance of WBDFs containing fluid loss agents. − The usage of cellulose, humic acid, modified starch type, and other filtration volume-reducing agents previously described, however, is now significantly limited since they are only applicable to shallower strata and cannot fulfill the need for high temperature resistance. Field experience has shown that the addition of starch may successfully reduce the filter cake’s thickness.…”

Research of Na2CO3/C12H25SO4Na modified bentonite on high dispersion performance

“…And Na-based bentonite was modified with HTAB. Because many quaternary ammonium cations were adsorbed on the surface of HTAB-bentonite, a decrease of the contact angle was found, which suggested an increasing affinity for oil, besides the rheological properties of the bentonite fluid easily affected by temperature [4]. When YI, et al [5] modified clay with nonionic surfactants, they found that the advantage of nonionic surfactants over ionic ones is that they improve the thermal and chemical properties of organoclays, and are also more readily biodegradable.…”