t a producing well and obtain relevant data from the test.
- Characterize reservoir such as permeability, skin and formation capacity.
- Estimate average reservoir pressure and define reservoir limit.
1.4 Relevance Of Study
- Prevent wrong decision making as a result of accurate estimation of well and reservoir properties.
- Help monitor reservoir and well performance.
- Detect possible causes of performance deviation.
- Data obtained will help in reservoir surveillance, input into reservoir simulation study and for production optimization.
1.5 Scope of study
This study is basically carried out to characterized reservoirs in terms of permeability, skin estimate to know if the wells are damaged or ascertain the success of stimulation jobs. Also determine the average pressure and drainage volume with the use of well test analysis software “Saphir”. Because of the difficulty of getting data from the industry, only build up will be analyzed.
1.6 Project outline
The outline of this thesis is in five chapters. Chapter 1 gives an introduction to the whole work which includes the aim and objectives, the scope and the relevance of the project. Presented in Chapter 2 is an extensive literature survey on the process route involved in pressure transient analysis. It looks at well testing, operation of Saphir software and interpretation of results. Chapter 3 presents the collected data and the sequential procedure by which these data were implemented in SAPHIR as well as figures for clarity of such processes. The results obtained from pressure transient analysis using SAPHIR and the discussion on how it monitors reservoir performance and well deliverability makes up Chapter 4. The conclusions made after analyzing the final results and future work recommended for further investigations are stated in chapter 5.
Conclusion And Recommendation
Two dual string oil wells were tested and the resulting data run in a tool (Saphir) to obtain reservoir characteristics such as permeability, skin and formation capacity as well as reservoir extent and initial pressure. These results are shown in table 4.1. This fulfils the aim and objective of this work.
Saphir, the software used for the analysis is very user friendly and timely. It is also accurate and informative compared to manual calculations and plotting.
Bottom-hole flowing pressure of the wells was determined using equation 4.2 at the operating rate. Bottom-hole flowing pressure for 2L, 2S, 3L and 3S are 175.374, 5,991.85, 515.472, 709.356psia respectively.
The skin found showed a negative effect on the production rate for S>0 and positive effect for S<0. Stimulation was proposed as a remedial action for the formation damage.
Significant increase in production rate was observed for possible stimulation effect on the damaged wells. Three wells were proposed for stimulation with 2L being badly damaged and 3L and 3S slightly damaged. The slightly damaged wells (3L and 3S) need not be stimulated immediately but future plans and provision should be made to avoid drastic drop in rate. 2L needs adequate stimulation to increase the flow rate. 2S shows stimulation has been done and successful with S= 3.33.
An assumption of reduced skin value after successful stimulation was made to prove the effect of stimulation on production rate. For well 2L, skin was reduced from 45 to 15 showing an increase in production of 963.757bbls (130.835% increase) at its flowing bottom-hole pressure. For well 3L, skin was reduced from 6.65 to 2 showing an increase in production of 665.965bbls (46.82% increase) at its flowing bottom-hole pressure. For well 3S, skin was reduced from 1.94 to 0 showing an increase in production of 314.941bbls (24.465% increase) at its flowing bottom-hole pressure.
The tool used (Saphir) is not 100% accurate, a better software should be used to analyze well test data which does not require excessive modification of result during analysis.
Further studies should be conducted to determine the best stimulation method that is cost effective and delivers a high rate. The quantity of materials requ