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Prevention of Emulsion Formation During Matrix Acid Stimulation Jobs Using A Multi-Node Injection System and a pH Buffering Complex. Abstract A perennial problem during matrix acid stimulation jobs is the prevention of emulsion formation during pumping of the acid treatment downhole and during flowback of the spent acid returns up the wellbore and through the production facilities to the storage tanks. The presence of emulsion commingled with crude oil in the storage tanks decreases the volume of the crude oil available for sale and also affects the logistics of storage tank volume available for incoming crude oil. During normal non-acid production periods, various chemicals are routinely injected both at the production platform and the fluid collection, separation and storage terminal. However, during the flowback of spent acid returns from matrix stimulation jobs, the tendency of emulsion formation from the wellbore to the terminal is extremely enhanced and very sensitive to certain system parameters. If the system parameters are not fully understood and controlled, the result of emulsion formation is invariably catastrophic. This paper presents the results of three years of study into the subject of emulsion prevention and control during matrix acid stimulation jobs in the Teak, Poui and Samaan fields, offshore Trinidad. The salient system parameters from the wellbore to the terminal which affect emulsion formation are presented. A unique Multi-Node Fluid Injection System, developed and utilized in Trinidad for the total control of the system parameters is also presented. Another aspect of this paper is the discovery, by the authors, of the application of a pH Buffering Complex to provide the ultimate method (to date) to control the formation of emulsion along the production system. The combination of the Multi-Node Fluid Injection System. and the pH Buffering Complex offers the best solution to date for the prevention and control of emulsion formation during matrix acid stimulation jobs. Introduction The Teak A, Poui A and Sarun A production platforms are approximately 40 km, 19 km and 45 km respectively off the South East coast of Trinidad. The Teak A production platform processes oil produced from five (5) platforms in the field. The Samaan A platform processes oil from three (3) platforms and the Poui A facilities from two (2) platforms. After acid stimulation jobs, severe emulsion problems can occur at the production facilities, both offshore and at the tank farm, Galeota Point, Trinidad. Offshore, the difficulty in fluid separation resulted in extreme work scheduling on the production pumps and in some cases, environmental concerns with the dumping of water overboard. At the Galeota Point base operations, the problem could result in thousands of barrels of oil being "tied-up" in the form of emulsions in the storage tanks, which affects crude oil sales and shipment. Test samples taken from the production system showed that in some cases emulsions were being produced from the well. in some cases, the degree of emulsion decreased upon neutralization. In other cases, the quantity of emulsion increased or actually developed upon neutralizing. In all cases, spent acid returns were neutralize using Soda Ash or Caustic Soda solution. Typical spent acid returns consisted of o to 3 percent HCl acid. P. 391
- Europe > Norway > Norwegian Sea (0.44)
- North America > Trinidad and Tobago > Trinidad > North Atlantic Ocean (0.34)
- North America > United States (0.28)
- North America > Trinidad and Tobago > Trinidad > North Atlantic Ocean > Columbus Basin > TSP Block > Teak Field > Moruga Formation > Gros Morne Formation (0.94)
- North America > Trinidad and Tobago > Trinidad > North Atlantic Ocean > Columbus Basin > TSP Block > Samaan Field > Moruga Formation > Gros Morne Formation (0.94)
- North America > Trinidad and Tobago > Trinidad > North Atlantic Ocean > Columbus Basin > TSP Block > Poui Field > Moruga Formation > Gros Morne Formation (0.94)
- (4 more...)
Design, Execution and Evaluation of Matrix Acid Stimulation Jobs using Chemical Diversion and Bullheading. Abstract A successful matrix acid stimulation job depends on various critical factors from the design of the treatment to the actual on - site job execution. Post job evaluation is also essential to learn from any shortcomings for the benefit of planning future jobs. The technical literature on the subject of matrix acid stimulation is very extensive. However, it is extremely difficult to locate material which describes the 'art' of the subject, rather than discussions on the science of separate aspects. This paper presents valuable information to practicing engineers on the salient features to be considered when designing, executing and evaluating a matrix acid stimulation job. There has always been much debate on the relative merits of bullheading a matrix acid stimulation treatment with chemical diverters versus the placement of the acid treatment via coiled tubing. The authors agree that the acid design and job execution must be dictated by the particular 'well specific' situation. However, the authors' mega success with the bullheading technique provided the basis for this paper. The engineering techniques leading up to a successful matrix acid stimulation job by bullheading with chemical diverters are revealed from the authors' experience. An actual case example is illustrated together with engineering design techniques for the removal of various types of formation damage. Introduction Matrix acidizing is a stimulation technique involving the injection of an acid solution at pressures below the parting pressure of the formation. The objective of the exercise is to remove any formation damage which is determined to be present in the near wellbore area, thus restoring the well to its true productivity. The presence of formation damage could be determined by the separate or combined use of evaluation tools, such as pressure build analysis, flowmeter data and temperature surveys (more generally, production logs). The presence of formation damage could also be determined by analysis of a series of field data. When injected into the formation, the acid dissolves the damage and some of the minerals present in the near wellbore area and hence restores all or a fraction of the original permeability. In limestone reservoirs, original permeability could be enhanced from acidizing. When compared to other oilfield operations such as hydraulic fracturing, significant failure rates have been reported for matrix stimulation applications. The only reliable means of measuring the effectiveness of a stimulation technique is to prove that the technical and economic objectives were achieved. The technical aspect deals with being able to reduce the skin factor (s, representing the formation damage) to a minimum value (ideal is s = 0) efficiently from the whole exposed pay, especially in multilayered reservoirs. When an operator can show negligible skin factor over all perforated intervals following a matrix stimulation job, the technique adopted (fluids, additives, and operating procedures) was undoubtedly the right one for the situation. Historically an acid treatment was regarded as a relatively cheap operation. As a result, few efforts to improve acidizing technology were undertaken. However, the industry's position has significantly changed due to the ever increasing number of wells to be stimulated in general, partly from the need to optimize well performance. P. 361
- Geology > Mineral (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (0.47)