The well drainage pressure and radius are key parameters of real-time well and reservoir performance optimization, well test design and new wells' location identification. Currently, the primary method of estimating the well drainage radius is buildup tests and their subsequent well test analysis. Such buildup tests are conducted using wireline-run quartz gauges for an extended well shut-in period resulting in deferred production and risky operations.
A calculation method for predicting well/reservoir drainage pressure and radius is proposed based on single-downhole pressure gauge, flowing well parameters and PVT data. The proposed method uses a simple approach and applies established well testing equations on the flowing pressure and rates of a well to estimate its drainage parameters. This method of estimation is therefore not only desirable, but also necessary to eliminate shutting-in producing wells for extended periods; in addition to avoiding the cost and risk associated with the wireline operations. The results of this calculation method has been confirmed against measured downhole, shut-in pressure using wireline run gauges as well as dual gauge completed wells in addition to estimated well parameters from buildup tests.
This paper covers the procedure of the real-time estimation of the well/reservoir drainage pressure and radius in addition to an error estimation method between the measured and calculated parameters. Furthermore, the paper shows the value, applicability and validity of this technique through multiple examples.
Al-Farhan, Farhan A. (Kuwait Foreign Petroleum Exploration Co) | Gazi, Naz H. (Kuwait Oil Company) | Al-Humoud, Jamal (Kuwait Oil Company) | Tirkey, Naween (Kuwait Oil Company) | Haryono, Rafiq (Kuwait Oil Company)
Interference testing, although primitive in terms of its introduction and idea to the petroleum industry, still stands to this day as one of the most cost effective and efficient ways of confirming communication and evaluating reservoir properties between wells. Similarly, a pressure build-up is one of the most accurate ways of estimating dynamic reservoir parameters surrounding the well, providing that the shut-in of the well is allowable. On the other hand, a drawdown test is not usually recommended due to the instability of the flow rate, and hence, the uncertainty in the parameter estimation when analyzing the transient of the pressure drawdown. In this project, due to production constraints a drawdown test was run for the active horizontal well as a substitute to the pressure build-up. It was therefore decided to couple the drawdown test with an interference test so as highlight the subsurface uncertainties. In order to achieve these objectives, careful design and operational coordination between the different asset teams and contractors is crucial to obtain interpretable and useful data.
Water production was observed in some of the nearby wells, and therefore communication between the horizontal well and the surrounding wells needed to be verified. The main objective of this project was to evaluate the reservoir parameters and connectivity surrounding the important horizontal well. In this test, the horizontal well was the active well in a five well interference test. The results of the test indicated different pressure behaviors seen from the observation wells corresponding to the pulse created by the horizontal well. Communication was established in some of the wells, whereas, faults were also verified in the surrounding regions. In addition, the drawdown analysis of the horizontal well showed all the flow regimes that relate to a horizontal wells' signature as well as boundary behavior which coincide with the interference test results. The results of the drawdown analysis indicate the possibility and accuracy of conducting a pressure transient analysis using this method without being constrained with production objectives, and hence not shutting the well in.
In the last decades, the major oil companies have moved aggressively toward challenging targets such as deep and ultra-deep water environments to increase their hydrocarbon reserves portfolio.
To deal with these new targets, attractive but located in harsh environments, technology has to improve significantly as well as the attention to be paid to operate under safe conditions. Operational daily costs are generally huge, sometime in excess of 1 million US$. As a consequence, the goal is to achieve a satisfactory balance between the value of information about the reservoir to be investigated and the ability to operate in a cost-effective manner.
The option of capturing real time downhole P&T data by using electric cables when testing an exploration well is considered less and less attractive due to intrinsic safety risks. This has triggered significant developments in the wireless technology in recent years. Real time data are transmitted acoustically, removing the need for wireline operations.
This wireless technology proved to be very effective increasing the test efficiency, optimizing the test sequence to acquire the well/reservoir response, minimizing costs and operating in a totally safe way.
A real field application on an offshore exploration gas well is presented in this paper. The test offered the opportunity to assess both benefits and limitations of the technology.
Bouziane, Chakib (NOV Downhole Tools & Pumping) | Bates, Paul Christian (Baker Hughes Oasis) | May, Norman (National Oilwell Varco) | Nicholl, Denise Stephanie (NOV Downhole Tools & Pumping) | Burnett, Timm Gleen (E on Ruhrgas EP GmbH) | Minardi, Andrea | Schlichting, Freya | Benmohamed, Mohamed Heidi | Bennati, Simon | Angeletti, Paolo
The majority of wells drilled in Algeria are vertical with three hole sections 16, 12¼ and 8½ inches. The main challenge in these applications is the ability to manage the drilling system for optimal performance by drilling efficiently minimizing both drill string component and well bore damage. The highly interbedded and variable compressive strength of the formations make the system prone to severe vibrations.
Vibrations are generated down hole while drilling. There are three types of vibration modes and they follow in order of severity, axial, torsional, and lateral. Lateral vibration is the most destructive mode and can create large shocks down hole with the Bottom Hole Assembly (BHA) components impacting the wellbore wall. The design of the drilling system should maximize the transfer of all the energy put into the drilling system drilling the hole rather than vibration. The anti-vibration sub is a tool designed to benefit the drilling by mitigating lateral vibration as part of the required energy management for efficient drilling. This has been observed through downhole data as well as Mechanical Specific Energy (MSE) comparisons.
Unlike traditional stabilizers, the near bit anti-vibration stabilizer acts more like a stabilizer and a centralizer while not generating point loaded blade friction associated with traditional stabilizers. The system has been introduced successfully on rotary BHAs with all types of drill bits. The cost per meter has been reduced while improving borehole quality thus reducing associated non-productive time required when conditioning the hole prior to setting casing.
This paper presents the field data acquired which indicates the importance of choosing the correct type, dimensions, and placements of the anti-vibration stabilizer. This anti-vibration stabilizer has been successfully utilized in several applications and is currently standard equipment for most vertical wells with rotary BHAs in Algeria.
Numerical analysis based on the non-linear dynamics method (AUTODYN) is performed to simulate the cracking processes in rocks containing a single pre-existing flaw. The dynamic analysis considers the interaction of the material with the stress wave, which propagates from the pressure boundary towards the model interior. The numerical results presented are based on the Drucker-Prager strength model along with the cumulative damage failure criterion.
The resultant crack types, crack initiation sequences and overall crack pattern are found to vary with loading conditions. Under a relatively low loading rate or a small magnitude of maximum loading pressure, tensile cracks tend to initiate prior to shear cracks. In contrast, under a relatively high loading rate and a large magnitude of maximum loading pressure, shear cracks tend to initiate prior to tensile cracks instead. Besides the loading rate, the maximum magnitude of the loading pressure is also found to influence the crack pattern. When the magnitude of maximum loading pressure is small enough, even if the loading rate is very high, the tensile cracks will initiate first and even no shear crack will initiate. To conclude, the crack pattern caused by quasi-static load can be expected to be very different from the that caused by high speed impact load.
The Martin Linge field was discovered in the 1970's but never developed due to a number of uncertainties. The complex structural settings of the Brent reservoirs was the main issue: transmissibility through the numerous faults has a direct impact on the number and type of development wells required for an appropriate drainage of the field, hence on the economy of the project
In 2009/2010 Total drilled an innovative appraisal well to de-risk this challenging development. The primary objective was to evaluate the dynamic connectivity through faults on the Upper Brent level of Martin Linge East with an Extended Well Test (EWT)
A program for the EWT (6 months duration), was defined and implemented in order to ensure conclusive results for the development strategy.
The well design included an innovative completion system with acoustic wireless down-hole gauges and a communication system to transfer the pressure data up to sub-sea well-head and then to shore via a communication link. This made it possible to obtain extended pressure build-up data after the rig had left. The test targeted the uppermost Brent reservoir of Balta only.
Analytical models were used to evaluate the investigated volume. This volume turned out to be significantly greater than the Balta reservoir accumulation, proving that the faults allow communication not only laterally but also vertically with the underlying Upper Brent Tarbert reservoir.
Due to the structural complexity of the field and the large investigation, the Eclipse reservoir model was also used to match the EWT data with the earth model. The EWT simulations in this model highlight the high lateral and vertical connectivity through major faults.
Al-Farhan, Farhan A. (Schlumberger) | Gazi, Naz H. (Kuwait Oil Company) | Al-Naqi, Meqdad (Kuwait Oil Company) | Ali, Farida (Kuwait Oil Company) | Dashti, Laila (Kuwait Oil Company) | Al-Qattan, Abrar (Kuwait Oil Company)
Interference testing although primitive in terms of its introduction and idea to the petroleum industry, still stands to this day as one of the most cost effective and efficient ways of establishing communication between wells and determining the reservoir transmissibility in the region.
This paper discusses the methodology and results obtained from a four month pressure data acquisition campaign for a transient interference test performed in a carbonate reservoir known as Marrat, in the Giant Burgan field of Kuwait.
The Marrat long term interference test was conducted around a water injector pilot with distances as far as 0.9 km at the subsurface locations between the injector and producer wells. Therefore, the interference test was used to evaluate the transmissibility between the injector and the nearby observation wells. The producer wells were shut-in for the entire length of the test so as not to create any disturbances that could hinder the interpretation processes. After conducting this test, a better understanding of the subsurface uncertainty as well as communication between the wells was highlighted. Other objectives were added to the tests which were to determine the water bank distance from the injector, as well as to describe the least resistive path that the water prefers to travel in.
The tests showed that not all the wells responded to the pressure pulse, and therefore the assumption that a fault was isolating one of the wells. One of the main conclusions was a strong directional transmissibility that was at first associated with a high permeability corridor corresponding to the depositional environment. The other conclusion was the orientation of the fracture plane which could cause this high directional transmissibility. A comparison and integration of the acquired pressure data with a separate geologic stochastic model was constructed and discussed in this paper.
Based on the integration work of the interference test and the geologic study it was therefore concluded that a secondary recovery using water flooding would be beneficial and necessary for sustaining Marrat reservoir production in the long term based on the location of both producer and injector wells.
Kawai, Hiroyasu (Marine Information Field, Port and Airport Research Institute) | Satoh, Makoto (Tohoku Regional Development Bureau, Ministry of Land, Infrastructure, Transport and Tourism) | Miyata, Masafumi (Ministry of Land, Infrastructure, Transport and Tourism) | Kobayashi, Takashi (Ministry of Land, Infrastructure, Transport and Tourism)
The 2010 Chilean Tsunami was observed on the Japanese coast by 11 GPS buoys of NOWPHAS (Nationwide Ocean Wave Information Network for Ports and Harbours); these buoys measured the water level by using real-time kinematic GPS technology at a water depth of 100 to 300 m. The highest tsunami crest was 0.1 to 0.3 m, and the predominant period was longer than 50 min. Owing to the coastal bathymetry, tsunami components longer than 30 min at the GPS buoy sites appeared amplified to nearby seabed wave gauge sites at water depths of 30 to 50 m, and the shorter components of 10 to 20 min appeared significantly amplified at the coastal tide gauge sites.
Since 1970, Japan’s Ports and Harbours Bureau, Ministry of Land, Infrastructure, Transport and Tourism and its associated organizations, including the Port and Airport Research Institute, have been conducting wave and tide observations around Japan as well as central data processing and data dissemination through the Nationwide Ocean Wave Information Network for Ports and Harbours (NOWPHAS) (Nagai et al., 2008). The data accumulated through NOWPHAS include not only high-wave events, but also the tsunami triggered by the 1983 Nihonkai-Chubu Earthquake, the 1993 Hokkaido-Nansei-oki Earthquake, the 1996 Irian Jaya Earthquake, the 2003 Tokachi-oki Earthquake, the 2004 Tokaidooki Earthquake, the 2005 Miyagi-ken-oki Earthquake, the 2006 Kuril Islands Earthquake the 2010 Central Chile Earthquake and the 2011 Earthquake off the Pacific Coast of Tohoku. NOWPHAS started with seabed wave gauges and coastal tide gauges in 1970 and introduced new equipment—GPS buoys—in recent years after a research team successfully used an experimental stand-alone GPS buoy to acquire data on the tsunamis triggered by the 2001 Peru Earthquake, the 2003 Tokachi-oki Earthquake and the 2004 Tokaido-oki Earthquake (Kato et al., 2005; Nagai et al., 2005a and b, 2006a, 2007).