Edgar Almanza

New Reservoir Testing and Sampling System Reduces Costs and Provides Improved Real-Time Data Acquisition in Deep Water and Environmentally Sensitive Wells ― Gulf of Mexico and Brazil Case Histories

The use of drill-stem testing (DST), particularly in offshore environments, has seen a marked decline in recent years. Several factors such as escalating rig rates, environmental concerns, personnel safety, and drilling-rig deck-space requirements have been responsible, but other factors have also contributed to this decline. Other testing methods have been developed that have been capable of providing certain types of reservoir information more cost efficiently and during a shorter period of time. This paper discusses a new type of system that allows a prospect to be sampled and tested without the necessity of a comprehensive and extended well test, or the testing process can be used as a first testing phase to be followed by a complete DST or production test, if necessary. Since closed-chamber tests were introduced in 1977, variations of this testing technique have been used to provide good flow estimations and basic reservoir parameters, although build-up data with short producing times were difficult to analyze. Combining this method with back surge proved to be very useful for perforation cleaning. However, some conventional sampling and data-collection systems in heavy oil and unconsolidated reservoirs have had limited success, resulting in decisions concerning assets to be made with limited information. The development of new bottomhole tools, either for testing or sampling, as well as real-time data acquisition systems and bottomhole data analytical methods are now available for short-time tests and offer an alternative for reservoir testing that can be completed in shorter testing times and are environmentally acceptable. They are also more effective in a broader scope of environments. The focus of this paper is one of these techniques that can be used in prospects where: • Expected production does not support the implementation of full-scale well-test evaluation and the data provided can be used to properly design an operation for full evaluation. • Environmental issues limit the oil and gas flaring as in some offshore wells or rain-forest locations. • Remote locations are not conducive to equipment transportation or have limited footprint. This document describes the first jobs performed with this limited-emission system in deepwater Gulf of Mexico in heavy-oil unconsolidated sandstone and in high-viscosity oil environments in Brazil. No safety incidents and no environmental incidents occurred. The system successfully captured bottomhole samples with pressure-volumetemperature (PVT) quality and sufficient reservoir information to calculate reservoir pressure, relative permeability, and radius of investigation on both cases presented. Both examples met all test objectives and demonstrated the advantages of the system. Introduction Traditionally, fully blended DSTs have been used to acquire bottomhole pressure and temperature and perform sampling operations. The system described in this document minimizes the potential environmental impact from surface fluid handling during these operations, making the work more environmentally friendly, reducing risk, and increasing safety. In addition, the use of the advanced sampling and data-collection systems now available for heavy oil and unconsolidated reservoirs has increased the performance of data acquisition and characterization information.

First underbalanced coiled-tubing-conveyed perforating operation performed in an HP/HT highly deviated well in East Venezuela

The technology for coiled-tubing-conveyed perforating (CTCP) under extreme conditions has been available for a number of years, but until recently, the techniques have not been used in Venezuela. This paper will describe the first experiences in which CTCP has been used in this area. The first candidate identified for the application was a new well in East Venezuela. This well was the first high pressure, high temperature (HP/HT) highly deviated deep monobore well completed in El Furrial Field in the North Monagas area that was perforated underbalanced with this technology. Although several traditional perforating methods were initially evaluated, the decision was made to perform the operation underbalanced using rig-assisted coiled-tubing technology because of the following advantages that could be realized from use of this method ○ Debris in the tunnel would be reduced, minimizing the potential for formation damage. ○ The debris could be circulated out more easily. ○ The use of kill fluid to control the well would not be necessary. ○ By eliminating the cost of the kill fluid and the resulting costs of handling the returned kill fluid, well costs would be reduced, The operation was performed in a live well with a 77-degree maximum well deviation and total depth (TD) of 17,907 feet. Several engineering simulations were performed before the job. These simulations enabled the operator and service engineering personnel to quantify the effects of CT fatigue, lockup, stresses, forces, elongation due to weight and temperature, and buoyancy effects. Other important factors considered were safety, health, environment, quality and well control, taking into account all possible contingencies. Finally, nine (9) coiled tubing runs were performed to complete the well, a total of 1,190 ft of 3 3/8-in., 6 shots per foot (SPF) and 2 3/4-in., 6 SPF guns were run. In all of the coiled-tubing-conveyed perforating runs, the expended guns were retrieved successfully under live well conditions. To retrieve the guns without killing the well, a subsurface flapper-type safety valve, which enabled the operations to be performed under controlled conditions, was used. Currently, the well is producing 19,621 BOPD through a I-in, choke and 1,591 psi surface pressure. Production and wellhead pressure expectations for this well were exceeded.

An Innovative Rigless Method for Perforating, Evaluating and Stimulating a Live Well

As development of hydrocarbon reserves continues to move into deeper and more complex reservoir conditions, operators have found that conventional techniques for testing, perforating, and stimulating may not provide satisfactory results in severe well conditions. A method was developed to optimize well-testing operations, improve safety, and reduce costs without compromising the results by replacing traditional drillstem testing (DST) operations. The technique can eliminate the need to kill the well to retrieve the guns and provides flexibility to test, evaluate, and fracture treat the well.