Low density gas hydrate suppressive drilling fluids have been developed for deepwater applications. These fluids utilize low molecular weight organic compounds for gas hydrate inhibition. Fluid densities as low as 9. 11b/gal can be designed for fluids with gas hydrate suppression greater than 30 F relative to water. These fluids are especially suited for use when low fracture gradients are encountered while drilling intervals where gas hydrate formation in the drilling fluid is possible. In addition, these additives provide greater gas hydrate suppression to drilling fluids than that provided by conventional thermodynamic gas hydrate inhibitors. P. 201

New mud chemistry is shown to improve the efficiency of directional drilling with steerable motor systems in the slide drilling mode through improved cuttings management. Both laboratory drilling simulator results and field case-histories are presented documenting the effectiveness of this technology. P. 69

Differentially pressured stuck pipe is a serious problem in the Gulf of Mexico and other areas of the world which results in costly and lengthy time delays. For years diesel oil, mineral oil, and mixtures of these oils with surfactants, clays, and asphalts have been spotted to help alleviate differentially pressured stuck pipe. With the advent of the Environmental Protection Agency's National Pollutant Discharge Elimination System (NPDES) General Permit on July 2, 1986 and the ending of the Diesel Pill Monitoring Program (DPMP) on September 30, 1987 the use of these conventional spotting fluids is becoming more stringently controlled in the offshore waters of the United States. In fact, after the use of conventional spotting fluids, the entire mud system may have to be sent ashore for disposal since offshore discharge is not allowed. In an effort to provide an environmentally acceptable alternative to oil based spotting fluids, a laboratory procedure was developed and used to measure the ability of various chemicals to free a metal bob held in a filter cake by a differential pressure. After the effective additives were identified, a few were selected for bioassay. One water-soluble agent, in addition to being highly effective in the stuck pipe simulation test, had a very low order of toxicity. This material was formulated into an experimental spotting fluid that successfully freed a differentially stuck drill string in the Gulf of Mexico. The development of a non-oil, low toxic spotting fluid has provided a suitable alternative to conventional spotting fluids resulting in an effective and environmentally safe way to combat differential pressure sticking of the drill string.

In the Gulf of Mexico and other parts of the world, bit balling and differentially stuck pipe has resulted in lengthy and costly drilling delays. In recent years the most effective mud system to combat these problems has been oil-base muds. Oil muds provide superior shale inhibition characteristics and excellent lubricity. However, due to increasing environmental concerns and regulations, in certain cases oil muds have become unacceptable options. Viable water-base alternatives, on the other hand, have been developed to incorporate the desired inhibitive and lubricous properties associated with oil-base muds without the problems associated with disposal. Recently an operator planned an offshore Louisiana multi-well program of directional wells through depleted sands. Past problems in the area include bit balling in hydratable shale sections and differentially stuck pipe in subnormally pressured zones. Until recently oil muds have provided the only solution. After researching the field and testing various inhibitive water-base fluids, the operator implemented a polyglycol (PPG)/aluminum complex water-base system. This system imparts lubricity and shale inhibition characteristics approaching that of an oil-base mud but without the environmental liability. To date nine wells have beep successfully drilled with the PPG / aluminum complex fluid with no occurrence of stuck pipe, bit balling, or wellbore instability. Additionally, the operator has been able to reduce its total well costs which can be attributed to the following: (1) reducing the number of bits, (2) reducing the number of drilling days, (3) reducing the size of the drilling rig, (4) eliminating the incidence of stuck pipe, and (5) eliminating disposal costs.

fax 01-972-952-9435. AbstractWater-based mud designs as alternatives to oil-based or synthetic-based muds are compared versus history of use. Water-soluble designs and water-insoluble designs are discussed as well as a combination approach used by Woodside Energy to drill on the Northwest Shelf, Offshore Australia. Perfornance of a water-based 2-phase polyglycol mud system containing a Drilling Enhancer with an appropriate bit design was technically and economically equivalent to that with a synthetic-based mud.