Charry, William M. (Hocol S.A.) | Rubiano, John (Hocol) | Beltran Lopez, Alexander (Hocol S.A.) | Velez, Maria Beatriz (Hocol) | Duarte, Anker Giovanni (Hocol S.A.) | Trujillo, Hernanado (Hocol SA) | Acosta, Wilson (Hocol SA) | Guerrero, Ximena (Schlumberger) | Penaloza, Javier (Schlumberger) | Florez, Darwin (Schlumberger) | Uribe, Roxana (Schlumberger) | Lopez, Nicolas (Schlumberger)
Oil production from the Llanos foreland basin in Colombia is seriously affected by sand production and high water cut. Sand production has been successfully controlled with horizontal openhole gravel packs; however, early water break-through causing water cuts as high as 90% remained a challenge. As a result, operators were forced to shut down some new wells just a few months after placing them on production. A new production logging approach was performed in five horizontal Hocol S.A. (subsidiary of Ecopetrol) wells. In terms of reservoir behavior, the results revealed the following:
With this new challenge in mind, a new sand control completion was developed with the following objectives:
The completion used a multizone, single-selective horizontal openhole gravel pack. The design was based on shunt-tube technology with swell packers as external isolation and a hybrid inner selective string design. The most innovative element of this completion was gravel packing of the entire completion to provide sand management, while offering the benefits of inflow control devices for water breakthrough management and selectivity. During the completion operation, the gravel-pack assembly was run and the rapid swelling swell packers were swelled using a new swelling fluid that allowed the swelling to take place before gravel packing the well. Once the swell packers were swelled, the gravel-pack operation began and it was confirmed that every segment was gravel pack, even after the swell packers were in place, thanks to the implementation of downhole gauges throughout the completion. Once the well was completed, the production group installed selective production and inflow control strings to produce the well.
The first completion installation was performed in July 2013. The operator performed characterization tests for each productive sand, with results for each sand indicating successful zonal isolation. The results also provided valuable data for reservoir characterization and selection of reservoir management strategies. The addition of new reserves confirmed the value and effectiveness of this new completion technology and its application.
The Ocelote field is located in the Llanos foreland basin of Colombia. The main production interval is the Carbonera C7 formation, which produces oil of 24°API with no gas production. The reservoir properties of Carbonera C7 include reservoir pressures of 1,643 psi, average temperature of 173°F, porosity of 20%, and permeability between 800 to 1500 md.
Pico, Antonio (Pacific Rubiales Energy) | Aboud, Jesús (Pacific Rubiales Energy) | Parraga, Felipe (Pacific Rubiales Energy) | Martinez, Jose Antonio (Pacific Rubiales Energy) | Lopez, Gonzalo (Pacific Rubiales Energy)
The central region of the Llanos Basin in Colombia has been characterized by an extensional structural style, where the overall fault pattern consists of normal faults oriented approximately N30°E, dipping East. The structures of the oil fields in Casanare Province have been defined by this type of faults. In this work we establish, for the Casanare Province, the existence of compartmentalized structures formed by the junction between N60° E en-échelon faults and N30E normal faults. In this interpretation, en-échelon faults and folds play a major role in oil accumulations. 3D seismic multi attributes, including volume curvature, coherency and ant tracking, were used to reduce the uncertainties associated with the seismic and well data in order to improve geological constraints, in folds, faults and associated fracture zones. As a result, a new strike-slip fault pattern was interpreted, consistent with a wrench zone, as proposed by Wilcox, et al (1973).
The Caracara Sur Field (Llanos Basin, Colombia) consists of multilayered compartmentalized fluviodeltaic reservoirs. Sands have Darcy-level permeability, contain a medium-quality oil (21º API), and are subject to very strong aquifer support. The reservoirs are produced with artificial lift, either selectively or commingled. After six years of development, oil production is expected to decline. Ongoing efforts to maintain the production plateau include infill and horizontal attic oil drilling and selective completions. However, there is a limit to what can be achieved considering the strong aquifer drive and unfavourable mobility ratio. This encouraged the investigation of enhanced/increased oil recovery (EOR/IOR) methods which has resulted in screening a number of EOR processes and the planning of a pilot project in the field.
EOR/IOR screening evaluation identified chemical EOR processes as the most suitable techniques for the field. Polymer, alkaline-polymer (AP), Alkaline-Surfactant-Polymer (ASP) and surfactant-polymer (SP) are the technologies under consideration.
A careful and complete project plan has been developed, customized for the field's most challenging characteristics: fresh formation water, in-situ oil viscosity of 12 cP, relatively high reservoir temperature (above 175 oF), the need to inject and produce commingled, (up to six stacked reservoirs) and most importantly the strong and drifting aquifer, which is expected to influence sweep efficiency.
The plan includes laboratory studies, multi-scale high-resolution reservoir simulation, single-layer single-well tests of injectivity and residual oil saturation, and a multi-layer inter-well pilot prior to full-field deployment. Tracer technology has been developed in-house to support the project. Back flow tracer tests and single-well tracer tests will be conducted in the field to evaluate aquifer drift and to determine the remaining oil saturation. Comprehensive evaluation will permit the design of an efficient vertical injection profile, appropriate injectivity and chemicals displacement in a multi-reservoir field.
The planning stage of the Caracara Sur EOR strategy, including the screening evaluation and the first project results, provides guidelines and solutions that can be used on other EOR projects in similar fields and facing similar challenges, not only within the Caracara Block itself, but within the Llanos Basin and elsewhere:
1. A ‘fast-track' program, whereby screening and field studies are done partly in parallel targeting shortened elapsed time for the pilot evaluation. If results are technically successful this will allow profitable full-field EOR implementation.
2. Use of an in-house project team supported by integrated laboratory expertise (leveraging CEPSA's petrochemicals experience) is proving to be efficient and successful in delivering a high quality technical solution.
Location and Regional Geology
The Caracara Sur Field is situated in the southern part of the Caracara concession, Llanos Basin, Colombia (Figure 1). The field consists of multiple stacked Tertiary reservoirs, which are, like many Llanos Basin fields, characterized by strong water drive and an unfavourable mobility ratio.
Gravel packing is one of the commonly used sand control techniques in long openhole horizontal completions. Although numerous wells have been gravel packed with either one of the two placement techniques (a/ß or shunt tubes), achieving a complete pack with sand control screens that have inflow control devices (ICD) can be challenging to say the least. This is because of the high pressure drops needed for the fluid to flow through the ICD into the base-pipe/wash-pipe annulus at the typical rates used for gravel packing, resulting in significant pressure rise and exceeding the fracturing pressure of the formation. Although using a screen without an ICD at the bottommost joint would certainly allow the a-wave to reach the toe, the pressure buildup will occur as soon as the ß-wave proceeds upstream of that joint, which will either result in formation fracturing and bridging or significant rate reduction and a-wave height increase (near the heel first), both events resulting in a premature screenout.
Ocelote field in Colombia requires sand control, and gravel packing and standalone screens (SAS) have both been used in openhole horizontal completions in various parts of the field. An additional challenge in this field has been the premature water breakthrough from the aquifer leading to very high water cuts after only a few months of production. ICDs have successfully been implemented in SAS completions to address this challenge in other parts of the world. Similarly, gravel packing has been successful in controlling sand in parts of the field where SAS was considered unsatisfactory, although water cut in most of these wells increased to 70 to 90% after only 3 months of production.
In this paper, we present a novel technique for wells that require gravel packing for sand control and ICD functionality for managing water encroachment. Detailed in the paper is the first application of the proposed technique in Ocelote field, which resulted in 100% pack efficiencies using the water packing technique as well as significant reduction in water cuts, with substantial improvement in the project economics.
Hogg, Cliff (Weatherford International Ltd.) | Barker, Ron (Weatherford International Ltd.) | Valverde Penangos, Juan Carlos (Hocol S.A.) | Caceres Leon, Rodrigo (Hocol S.A.) | Gandara, Carlos Alberto | Ortiz Prada, Everardo | Gil Chipatecua, Paola Adriana | Rueda, Henry
Trujillo, Hernando (HOCOL S A) | Tengono, Jose Aldemar (HOCOL S A) | Rubiano, John (HOCOL S A) | Castaño, Ricardo (HOCOL S A) | Beltran, Alexander (HOCOL S A) | Ortiz, Everardo (HOCOL S A) | Navarro, Claudia (Schlumberger) | Florez, Darwin (Schlumberger) | Lopez, Nicolas (Schlumberger)
Trujillo, Hernando (Hocol S.A.) | Tengono, Jose Aldemar (Hocol S.A.) | Hernandez, Angel Enrique (Hocol S.A.) | Ortiz Prada, Everardo (Hocol S.A.) | Charry, William M. (Hocol S.A.) | Castaño, Ricardo (Hocol S.A.) | Anaya, Luis Antonio (BJ Services Company) | Portela, Jose Fernando (BJ Services Company) | Castillo, Rubén Darío (Ecopetrol S.A.) | López, Marco (Baker Hughes Inc) | Calderón, Carolina (Baker Hughes Inc)
Hocol Colombia operates in Ocelote field at the eastern part of Colombia, a land called as Llanos Orientales (Eastern Plains). In this field Hocol produced from Carbonera formation observing problems with formation deconsolidation. Normally, gravel packs jobs are performed on vertical wells with sustained good results.
However, new reservoir studies showed that horizontal wells with regular length extension (around 1000 ft) would be more profitable for this field. In order to get this objectives, Hocol design a horizontal wells Program to drill and test alternatives to get good completion of these wells. The first well was completed and gravel packed using conventional technologies and a 35% of pack efficiency was achieved.
The objective for the second well was to get at least 75% of packing efficiency. In a synergetic team effort, service companies proposed operator company new technologies that are used in other places but never were applied in Colombia. After simulations and technical meetings, the Operator decided to test two new technologies to try to get their operative and technical objective.
This paper presents the technical and operative fundamental used to support these changes and the results obtained with theses applications.
Last, N. (British Petroleum Exploration Colombia) | Plumb, R. (Schlumberger Cambridge Research) | Harkness, R. (University of Southampton) | Charlez, P. (Total Exploration Production) | Alsen, J. (Triton Energy Corp.) | McLean, M. (British Petroleum)
N. Last, SPE, British Petroleum Exploration Colombia; R. Plumb, SPE, Schlumberger Cambridge Research; R. Harkness, University of Southampton; P. Charlez, SPE, Total Exploration Production; J. Alsen, Triton Energy Corp.; M. McLean, SPE, British Petroleum
An integrated approach to evaluating the causes of severe wellbore instability in the Cusiana field is described. The field is located in a tectonically active region of Colombia. Deterioration of the hole during drilling operations has led to excessive nonproductive time and expensive wells. The scale of the problem is unprecedented in the world. In wells costing tens of millions of dollars, millions per well could be attributed to poor hole conditions.
This paper describes how the problem was addressed and what actions were taken to improve operational performance, resulting in reduced drilling costs. The improved understanding has contributed to better well planning, and improved drilling performance, and has underlined the need to consider all aspects of the drilling process to achieve improved hole conditions in a difficult geological setting.
Nature of the Problem. Major drilling problems have been encountered in the Cusiana field. The field is located in the Llanos basin (Fig. 1), a tectonically active foothills region of the Eastern Cordillera in Colombia. The biggest problems stem from hole enlargement (Fig. 2), resulting in large amounts of cavings, often measured in truck loads per hour, which cause hole cleaning problems, stuck pipe, poor cementing, and often the need to sidetrack. The added complication of severe hole rugosity (alternating in-gauge and over-gauge sections) through interbedded sand-shale sequences. as in (Fig. 3) makes tripping, running casing and logging problematic, and renders large amounts of reaming necessary.
The range of problems facing the drillers was formidable. Limited success was achieved by using experience from other parts of the world. For example, the use of higher mud weights, the conventional approach to solving hole enlargement problems, was unworkable because of the significant mud losses that occurred as the mud weight was raised. There was even some evidence that higher mud weights were accelerating the onset of poor hole conditions. Initially there was reluctance to accept the need for a new approach.
Geological setting. The main features of the setting are illustrated in Fig. 1. Although the geological history includes an initial period of extension (including contemporaneous extensional growth faulting), the current tectonic environment is characterized by active thrusting toward the southeast, the assumed direction of maximum horizontal stress, with the thrust front marked by the Cusiana fault. To reach the reservoir in the hanging wall of the Cusiana fault, most production wells must penetrate the hanging wall of the Yopal fault and cross the Yopal fault. Although not detailed in Fig. 1, numerous smaller faults in the structure complicate the lithological sequence (sections are repeated) and produce abrupt and frequent changes in bedding dips. As an example, Fig. 4 is a detailed section through well X.
Fig. 5 summarizes the generic lithological sequence. While problems have been encountered in most of the formations, by far the most problematic drilling has occurred in the alternating sand-shale sequence called the Carbonera In particular, losses and tight hole have occurred in the sandier units (C1, C3, C5 and C7), and wellbore enlargement has occurred in the shalier units (C2, C4, C6 and C8).
Approach to Solving the Problem. Concerns over the increasingly high drilling costs and the lack of progress toward improved hole conditions led to the establishment of a multidisciplinary, multicompany team with the responsibility to help reduce costs associated with wellbore instability. This objective was challenging given the complexity of the problem, an aggressive drilling schedule and the absence of hard facts needed to make convincing arguments for change. In the end a relatively simple solution emerged: namely, manage the instability rather than trying to cure it completely.