West Coalinga Field Research Articles

A structured approach to the diagnosis of formation damage caused by organic scale deposits and surface active agents, Part I: Development of a Diagnostic Process

Abstract A structured approach has been proposed for diagnosing formation damage caused by organic scale deposits and surface active agents. The approach is based on a comprehensive set of heuristic rules governing the formation of emulsions, water blocks, and wettability reversal as well as the deposition of asphaltenes and wax in hydrocarbon reservoirs. The compiled rules, representing experts' knowledge, have been derived from standard industrial practices and integrated with empirical models to ensure a robust view of the diagnosed damage types. The knowledge has been arranged in decision trees that form the core structure of a diagnostic process to identify types of formation damage. The damage diagnostic process is performed by walking through the history of the reservoir from drilling to production, stimulation, EOR processes, and workover jobs. The complete history of the well is carefully scrutinized for evidence of any field practices that might cause formation damage. The developed approach and knowledge has been tested with 3 comprehensive hypothetical cases that simulate a wide range of damage problems. This approach has also been validated with two documented field cases that involve producing wells in the West Coalinga field in California and in the Ghawar field in Saudi Arabia. Both cases resulted in thorough diagnoses of damage types in agreement with field observations. This paper forms the first leg of a two-part series: (I) Development of a Diagnostic Process, and (II) Expert System Development. Part I proposes a structured approach for diagnosing formation damage. Part II automates the diagnosis process developed in Part I.

ABSTRACT: Reservoir Simulation Using Fractal-Based Petrophysical Models of Heavy Oil Sands in West Coalinga Field, California

ABSTRACT: Reservoir Simulation Using Fractal-Based Petrophysical Models of Heavy Oil Sands in West Coalinga Field, California

Geologic study and multiple 3-D surveys give clues to complex reservoir architecture of giant Coalinga oil field, San Joaquin Valley, California

Coalinga is a giant oil field in the San Joaquin Valley of California (Figure 1) with an extremely complex subsurface stratigraphy, resulting in high operating costs relative to many other fields in the basin. Integration of stratigraphic interpretations based on core and outcrop with recently acquired 3-D seismic data and an extensive well log database enabled development of a sequence stratigraphic model encompassing the main producing reservoirs in West Coalinga Field. Our understanding of horizon maps and vertical reservoir connectivity has undergone significant changes, influencing development decisions for the field. Further integration of this new model with lithofacies descriptions, distributions, petrophysical, and production data are ongoing. Computer-based reservoir models for fluid-flow simulation and optimizing steam injection are being developed and hold additional promise for minimizing operating costs and maximizing production from this giant field. Figure 1. Proximity of Coalinga Field to the San Andreas Fault on the west side of the San Joaquin Valley. Lower to Middle Miocene strata are prolific hydrocarbon reservoirs in several San Joaquin Valley oil fields. On the west side of the valley, these rocks, called the Temblor Formation, have produced about 1.2 billion bo from several fields. Coalinga, by far the largest, has produced 850 million bo since 1887. Although recent development has significantly increased production from Pliocene sandstones of the Etchegoin Formation (Taschman, 1982), 90% of the current production is from nearshore to nonmarine, Middle Miocene sandstones of the Temblor Formation at depths of 500–4500 ft. Porosity averages 34% and permeability is 20–4000 millidarcies. Most reservoirs in the San Joaquin Valley are sourced by the Upper Miocene Monterey Formation. In contrast, Temblor Formation oil at Coalinga derives from organic-rich shales of the underlying Middle Eocene Kreyenhagen Formation (Peters et al., 1994; Clark et al., 2000). Although the field was discovered in 1887, significant production did not …

Abstract: Characterization of Miocene Temblor Formation, West Coalinga Field, San Joaquin Basin, California: Insights into the Stratigraphic Geometry of a Transgressive Reservoir

Abstract: Characterization of Miocene Temblor Formation, West Coalinga Field, San Joaquin Basin, California: Insights into the Stratigraphic Geometry of a Transgressive Reservoir

Abstract: Capturing the Geology Accurately in Alternative Reservoir Modeling Processes - An Example From the Etchegoin Reservoir at West Coalinga Field, California

Abstract: Capturing the Geology Accurately in Alternative Reservoir Modeling Processes - An Example From the Etchegoin Reservoir at West Coalinga Field, California

An Application of Crosswell Tomography Using a Hydrophone Receiver Array and Airgun Source to Monitor Steam Migration in-an Unconsolidated, Heavy-oil Sandstone, West Coalinga Field, California: ABSTRACT

This crosswell tomography field trial demonstrates the viability and cost- reducing benefits of a hydrophone receiver array and airgun source for monitoring steam (heat) migration within an unconsolidated, heavy-oil sandstone. This project represents one of the first applications of hydrophone receivers in such an environment. Data quality from the hydrophone array proved more than adequate for P-wave tomography while costs were reduced dramatically from estimates using a clamped geophone array. Additionally, the resolution provided by the capture of travel-time data from interwell areas offered a distinct advantage over conventional monitoring techniques limited to observation wells. Two crosswell surveys were conducted in the vicinity of a new, infill steam injector. The purpose was to monitor steam migration within an 80-foot thick, sandstone interval by detecting the heat-induced velocity decrease between the first survey, conducted just before steam injection, and the second survey conducted approximately three months later. Difference plots of the two surveys clearly define regions of significant temperature change and contact temperature logs corroborate the zone of peak change. The crosswell tomography data and the inferred steam migration characteristics immediately altered an operational strategy for the drive and were later a factor in the abandonment of continuous steam injection.

Water-Alternating-Steam Process Improves Project Economics at West Coalinga Field

Summary The water-alternating-steam process (WASP) was applied to vertical expansion (VE) sands in the pilot area of Section 13D, West Coalinga field to stop wasteful steam production and to improve vertical conformance of injected steam. Before the WASP application, steam breakthrough in the VE sands caused well sanding, cutting of downhole tubulars, and high-temperature-fluid handling problems. To alleviate these problems, pumps had to be raised in five wells and one well had to be shut in, reducing oil production from the VE sands and the lower waterflooded zones. A WASP field test, based on a numerical simulation study, was implemented in July 1988 with alternating slugs of water and steam, each injected over 4 months. The WASP eliminated steam production, allowing the pumps to be lowered and the one shut-in well to return to production. Oil production remained constant through the first WASP cycle and increased during the second cycle. Sales oil (total production minus oil used to generate steam) increased as a result of saving generator fuel during the water leg of each WASP cycle, resulting in improved project economics.