The need for environmentally acceptable cement additives has encouraged the development of new additives based on biopolymers, especially in the North Sea area where environmental regulations are very strict. The main challenge is to develop environmentally acceptable chemicals that meet the relevant environmental legislation and operational criteria, and thus could replace synthetic materials that are currently being used. This paper will describe the development of a cement fluid loss additive that meets the challenges described above. Cellulose-type materials have been used for decades as additives to control cement fluid loss. These are PLONOR (pose little or no risk) listed materials, which means they do not have to be subjected to testing protocols. They were agreed upon by all OSPARCOM (Oslo-Paris Commission) countries, and thus, required no further extensive ecotoxicity testing before introduction. However, cellulose-type materials that have been used so far have several limitations: their fluid loss control properties decrease at temperatures above 200°F, their salt tolerance is limited and over-retardation problems can occur at low temperature. Furthermore, the slurry viscosity to fluid loss ratio is unfavorable compared to that of currently available synthetic fluid loss additives. When these cellulose type materials are combined with other additives to help improve their performance, the environmental advantages are compromised, and the resulting substance can no longer be listed as PLONOR. This paper describes the development of a modified cellulose (HEC) type of cement fluid loss product. It is salt tolerant, it can perform well up to temperatures as high as 280°F and is environmentally acceptable. After extensive laboratory testing, the production has been scaled up for introduction and a successful field trial has been performed in the North Sea area. Background Information Ensuring that cement slurry performs according to design parameters can be essential for the success of any job involving cement. Obtaining an appropriate cement slurry can require intensive laboratory testing until the slurry design meets design specifications. The selection of a fluid loss additive is important for cement placement and zonal isolation. Fluid loss additives help prevent water loss from the slurry, and thus, help prevent cement bridging in the annulus. Restricting fluid loss also protects water-sensitive formations. Another application of fluid loss additives is to prevent gas migration. The transition of the cement slurry from a liquid to a solid phase causes the hydrostatic pressure to drop and can allow gas to percolate through the unset cement. By preventing leak-off of interstitial water to permeable formations the influx of gas can be reduced. To help protect the environment in the North Sea, the OSPARCOM has implemented a system called the harmonized mandatory control system (HMCS) regulating the use and discharge of offshore exploration & production chemicals1,2. According to previous OSPARCOM regulations, each country has the right to implement their own stringent requirements other than those provided in the OSPARCOM guidelines. More recently implemented guidelines introduce a pre-screening scheme3, which new products must pass, while products with certain unfavorable environmental properties are prohibited in the North Sea, or are given temporary permission for use. OSPARCOM countries like The United Kingdom, Norway, Denmark and The Netherlands all accepted the harmonized pre-screening system. According to OSPARCOM, the materials that are allowed for use in the North Sea need either to be PLONOR-listed or to pass the relevant ecotoxicity tests. The PLONOR list contains generally accepted non-harmful materials. If a material is not on the PLONOR list it needs to be ecotoxicologically tested with respect to biodegradability, bioaccumulation and toxicity. The ecotoxicological tests to be used are specified in the OSPARCOM guidelines.

Surface-active components in the form of intrinsic emulsifiers have been studied, and their possible role as demulsifiers has been assessed. Polar components were extracted from crude oil via three isolation methods involving liquid/liquid extraction at pH 14, liquid/liquid extraction at pH 1, and column chromatography. All three isolates were found to improve separation within hours independent of their concentration. The material isolated from acidic extraction was found to be the most efficient. An expanded chemical analysis of the isolates involving Fourier transform infrared spectroscopy, UV−vis spectroscopy, liquid chromatography–mass spectrometry, and liquid chromatography–tandem mass spectrometry analysis was employed to identify the polar compounds in the three isolates. The most polar components were found to be naphthenic acids and saturated and nonsaturated noncyclic carboxylic acids. The least polar compounds were found to be nitrogen-containing aromatic bases such as pyridines, quinolines, pyrroles, indoles, indolines, and carbazoles. A mixture of compounds with polarities between the acids and bases were identified as phenols, pyrans, benzopyrans, naphthopyrans, benzonaphtholpyrans, dibenzopyrans, dinaphthopyrans, and compounds containing both nitrogen and oxygen atoms. The fact that so many compounds are found in each extract makes it difficult to speculate on exactly what types of molecules are significantly contributing positively to the emulsion breaking and separation process. The suggested polar molecules from this work have been sufficiently precise for a follow-up study to be realistic and promising, where the dominating polar molecules in each category are synthesized and subjected to separation experiments. Finally, interesting observations were made that relate to oil maturity and origin.

This paper describes the design, development and application of a new sealant system for multilateral well junctions. The sealant system has been successfully applied in offshore multilateral well installations for North Sea operators. In recent years, the oilfield industry has shown an increasing interest in multilateral wells. Multilateral wells are an economically viable solution for many offshore operators because multilateral wells increase reservoir drainage and extend the wellhead slot coverage on offshore platforms. Multilateral wells can range from simple openhole completions to sophisticated cased-hole completions that have selective access to all laterals. In contrast to the openhole completions and slotted-liner completions, cased-hole completions enable the operator to have more control over production because cased-hole completions allow re-entry for perforating and production logging operations. However, zonal isolation is difficult to achieve at a multilateral junction where the hydraulic seal between the formation and the casing interior is maintained by the sealant only. The sealant system must be resistant to many destructive forces during completion and production. Mathematical models were used to quantify stresses that are exerted on the sealant during completion and operational processes in a multilateral well. A procedure was established to scale the stresses to laboratory conditions. Based on the procedures, it became apparent that the multilateral sealant required high elasticity and high impact resistance, as well as standard oilfield cementing properties. This paper presents how the sealant system was specifically designed and developed to meet the requirements of a cased-hole multilateral completions. Field jobs in which the sealant system was successfully placed are presented. These jobs show that the sealant system withstood stresses at the junction in North Sea multilateral completions. Introduction Multilateral wells have recently been developed to increase production. Multilateral wells can be vertical or deviated (including horizontal) wellbores connected to one or more subordinate laterals. Drilling and completion equipment have been developed that allow multiple laterals to be drilled from a main cased and cemented wellbore. Each of the lateral wellbores can include a cemented liner that is connected to the principal wellbore (Figure 1). Multilateral wells have been successfully drilled and operated; however, one operational problem involves zonal isolation of the multilateral junction. The casing and liners are cemented in the principal and lateral wellbores, respectively, by introducing cement slurries in the annular clearances between the walls of the wellbores and the casing and liners. In the past, conventional well cement slurries were used. Although cement is a strong material, it cannot withstand repetitive impacts and stresses that occur during drilling, milling and other well operations in the laterals. Once the set cement is shattered, it may allow leakage of fluid through some portions of the wellbores. Improved methods of cementing multilateral wells were necessary. A sealant research project was initiated to determine testing methods and fluid compositions. A number of test methods were used including API fluid testing, impact resistance tests and chemical resistance tests. The multilateral sealant required high elasticity and impact resistance. Therefore, a highly elastic sealant and a brittle sealant were chosen as extremes to guide the development of the multilateral sealant. Elastomer-based slurries were chosen for testing because they are known to provide high elasticity to set materials. P. 243^

For the past 20 years, there has been increasing global emphasis on development of environmentally acceptable materials to replace chemicals that are considered to be either toxic to flora and fauna or otherwise to pose a long-term hazard to the natural environment. However, globally accepted definitions for unacceptable toxicity or environmental hazard do not exist. Likewise globally accepted protocols for testing methods to evaluate these hazards do not exist. The Oslo-Paris Commission (OSPARCOM) was inaugurated in 1992 for the protection of the marine environment of the Northeast Atlantic. In 1998, OSPAR Conventions were ratified by Belgium, Denmark, the Commission of European Communities, Finland, France, Germany, Iceland, Ireland, Norway, Portugal, Spain, Sweden, the United Kingdom of Great Britain and Northern Ireland, Luxembourg, and Switzerland. The goals of the OSPARCOM are to prevent and eliminate pollution from land-based sources, dumping or incineration, and offshore sources, and to assess the quality of the marine environment. To this end, the OPSARCOM has initiated a series of stringent testing protocols that are used to evaluate chemicals that may be detrimental to the marine environment. Additionally, the Harmonised Offshore Chemical Notification Format (HOCNF), which must be completed on all chemicals to be registered for offshore use, has unified the reporting format. Elsewhere around the globe, the regulations on use of chemicals in the offshore environment are not as highly structured, and, generally, are less strict. For example, chemical discharges offshore in the Gulf of Mexico are based on oil- and grease-extraction tests and static sheen. Aquatic toxicity testing is usually required before discharge is allowed in the Gulf waters. However, these restrictions are rapidly changing and may become much more structured in the near future. This paper summarizes Halliburton's research efforts over the past several years to comply with, and preferably exceed, the diverse global regulations and guidelines in the areas of environmentally acceptable cement dispersants, retarders, viscosifiers, foamers, defoamers, fluid-loss additives, and spacer-blend additives. Introduction Recently, terms such as "environmentally acceptable," "environmentally friendly," "environmentally degradable," "environmentally compliant," "nontoxic," "green," "biodegradable," and "nonbioaccumulating" have become increasingly popular in describing environmentally safe products. However, none of the terms is universally defined, and as a result, much confusion exists about truly environmentally safe practices and products. This paper is not a review of the regulations that govern the use and disposal of chemicals around the world. However, it is necessary to describe some of the regulatory guidelines in practice and to define certain terms for clarity. OSPARCOM has compiled a list of chemicals that pose little or no risk (PLONOR) to the marine environment. Materials on this list may be used and discharged anywhere in the North Sea without further environmental evaluation. Materials that are not on the PLONOR list are subject to testing protocols that were agreed upon by all of the member countries of OSPARCOM and were described in Harmonized Offshore Chemical Notification (HOCNF) document. The HOCNF protocol requires toxicity testing on a variety of marine organisms. While all of the member countries of OSPARCOM have agreed to use the HOCNF guidelines, the final interpretation of the data and the ranking of individual chemicals for offshore use and discharge are performed by the regulators in each country.

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