Controlled injection at high rates predominantly under fracture regime has been identified at the onset of most waterflood field developments as being crucial to meeting the multiple objectives of pressure maintenance, voidage replacement, sweep optimization and injector longevity. In the vast majority of these developments, a deviation from fractured injection into matrix injection mode has been identified as a primary cause for the onset of injectivity decline. Identifying and clearly delineating injection regimes therefore presents an opportunity to arrest early decline. However the identification and delineation of injection regimes has remained a big challenge. This paper presents a high resolution and novel technique of delineating injection regimes. Traditionally LOTs, PFOs, SRTs and Mini-Fracs have been used to estimate fracture parameters in competent formations; however in soft Miocene reservoir systems that typifies the Gulf of Guinea depositional system most software and modeling workflow applied in classic fracture mechanics cannot and do not accurately model the mechanical behavior of these sediments under stress. While the Hall Plot has been widely applied in delineating changes in injection regimes (from fractured to matrix) it has the limitation of not been able to detect subtle changes in injection regimes over short time periods. This paper showcases a novel modification to the Hall plot to provide a high resolution delineation of injection regime. The second order derivative of the plot of the cumulative work per unit time versus the cumulative injection amplifies subtle variations in the performance of injection wells not discernible with the traditional Hall plot. This diagnostic plot when combined with other equally apt diagnostic plots such as a time-lapse plot of the reciprocal of injectivity decline will provide a definite identification of the prevailing injection regime. An added advantage of these plots is the ability to provide real-time detection of the onset of injection damage and also allow a comparison of damage signature across time intervals and across injection wells which could provide additional information as to the nature of the impairment. All these combined will facilitate early identification of possible damage mechanism and a quick response to injectivity decline in terms of topsides or downhole remediation. This technique was applied in the analysis of five injectors in a deepwater waterflood development in the Gulf of Guinea. The result was a clear and concise delineation of fracture and matrix injection regimes and the start of the transition period. Analysis indicated that early injection period had been predominantly under fracture injection for most wells (during the first 6–12months) while subsequent injection has been under brief spells of fractured injection followed by rapid transitions to predominantly matrix injection regimes which coincided with periods of injectivity decline. This diagnostic plot was also compared to the Hall plot and demonstrated that in the majority of cases, the changes in injector performance and injection regime starts way before it is detected by the Hall plot.
Overtime waterflood has proven to be the most versatile of reservoir development strategies as the relative flexibility, relatively mature technology and adaptability in a variety of environments and patterns makes it frequently the economic and safe option. This paper presents experiences garnered from a high resolution well and reservoir surveillance in a waterflood asset and clearly demonstrates that effective waterflood performance management is key to realizing the full potentials of waterflood developments especially in sedimentary systems with marked micro and macro stratigraphic and structural heterogeneities. Field W has been under waterflood for over twenty years and the recovery to date has more than doubled the initial depletion based estimate clearly demonstrating the widely proven benefits of waterflood developments. However poor injectivity, varying reservoir pressure and increased fracture growth have been recognized of late as major factors militating against effective water injection performance in the field. This paper will demonstrate the applicability of Hall's plot towards a robust well and reservoir performance monitoring and management in Field W. The conventional and primary use of the Hall plot has been to track the quality of water injection/or general performance in/of injectors, but it will be demonstrated that field trends of oil and water cut, interference testing, reservoir pressure evolution, static and dynamic formation evaluation data and the general reservoir drainage pattern can be better understood with development ambiguities greatly illuminated with the judicious use of the Hall plot integrated with other associated diagnostic plots. The paper will also clearly establish that for Field W the combination of the Hall plot techniques and other conventional waterflood diagnostic plots to field production data has significantly improved an understanding of field-wide well and reservoir performance, injector-producer pair interaction, effectiveness of injection regime/production policy, delineation of drainage patterns and a high resolution reservoir characterization for optimization of new well placements.
Production of lysine by Alcaligenes aquatilis from agricultural sub-products (banana and soybean) was compared to glucose and ammonium sulphate as a carbon and nitrogen source. Ammonium sulphate was constant as a nitrogen source when the two carbon sources were investigated and glucose constant as a carbon source when the nitrogen sources were investigated. The production of lysine was examined quantitatively by acidic ninhydrin method. The results showed that banana and soybean improved the maximum lysine yield (1.158 mg/ml and 1.279 mg/ml) for the fermentation period of 96 hrs.
The success of any green as well as mature field development planning and execution lies in the ability to recreate the environment of deposition with the appropriate spatial and temporal facies interdependencies. This, when done with proper application of the varied suite of geotechnical software/knowhow, often leads to the creation of a finite number of high resolution and equiprobable reservoir models within a macro and micro sedimentological framework, that readily lends itself to optimized risk and uncertainty management. This becomes even more critical in deepwater turbidite systems where the impact of geologic uncertainties can significantly reduce project value and does often prevent marginal field developments in the absence of a low cost tie-in option.This paper presents the novel application of one such technique; the QuantiMin methodology approach improves aspects of reservoir characterization and facilitates various aspects of well and reservoir management in the waterflood development of a Miocene deepwater turbidite system in the Gulf of Guinea.The QuantiMin technique is a sequential quadratic program that solves non-linear problems by series of quadratic programming steps. When applied in this context, it assesses the mineral and fluid content around the near wellbore area, based on their unique well log responses, and returns with a finite volume distribution of mineral and fluid distribution around the wellbore, using the mineral and fluid distribution input from appraisal well cores as the calibration or control variable.The results from QuantiMin analysis have been used in this field to: • Evaluate the potential impact of mineralogy on the performance of water injection wells. • Apply understanding of mineral types around the wellbore to the design of acid stimulation recipes. • Develop a framework for understanding the field scale distribution of heterogeneities by establishing the interdependencies between log-scale QuantiMin and microscopic core petrography data, and hence facilitate high resolution reservoir characterization. • Establish realistic flow potentials for development wells.
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